X52b-8y2Hf4.json

[
    {
        "text": "[MUSIC PLAYING]",
        "start": 0.0,
        "duration": 2.465
    },
    {
        "text": "DAVID MALAN: All right, welcome\neveryone to Mobile App Development",
        "start": 18.241,
        "duration": 2.799
    },
    {
        "text": "with React Native.",
        "start": 21.04,
        "duration": 0.93
    },
    {
        "text": "My name is David Malan,\nand this here is--",
        "start": 21.97,
        "duration": 2.04
    },
    {
        "text": "JORDAN HAYASHI: Jordan Hayashi.",
        "start": 24.01,
        "duration": 0.96
    },
    {
        "text": "DAVID MALAN: --and this\nis a course that assumes",
        "start": 24.97,
        "duration": 2.0
    },
    {
        "text": "as background only\nsomething like CS50, which",
        "start": 26.97,
        "duration": 2.204
    },
    {
        "text": "is Harvard's Introduction\nto Computer Science.",
        "start": 29.174,
        "duration": 1.916
    },
    {
        "text": "But more generally, if you haven't\ntaken that particular course,",
        "start": 31.09,
        "duration": 2.666
    },
    {
        "text": "prior programming experience in\nmost any language should suffice.",
        "start": 33.756,
        "duration": 3.424
    },
    {
        "text": "The focus of this class, of course, is\ngoing to be on mobile app development.",
        "start": 37.18,
        "duration": 2.46
    },
    {
        "text": "And the interesting\nthing about this space",
        "start": 39.64,
        "duration": 1.75
    },
    {
        "text": "is that it's been\nchanging pretty rapidly.",
        "start": 41.39,
        "duration": 1.937
    },
    {
        "text": "It wasn't all that long\nago where none of us",
        "start": 43.327,
        "duration": 1.833
    },
    {
        "text": "actually had smartphones in our pockets.",
        "start": 45.16,
        "duration": 1.959
    },
    {
        "text": "And so the landscape has been\nchanging, particularly quickly.",
        "start": 47.119,
        "duration": 2.541
    },
    {
        "text": "And it's getting better and better.",
        "start": 49.66,
        "duration": 1.53
    },
    {
        "text": "If you've done any app developments on\nmobile devices or any web development",
        "start": 51.19,
        "duration": 4.35
    },
    {
        "text": "on mobile devices,\nearly on we pretty much",
        "start": 55.54,
        "duration": 2.13
    },
    {
        "text": "just had HTML and CSS, maybe some\nJavaScript for interactivity.",
        "start": 57.67,
        "duration": 4.05
    },
    {
        "text": "Then lots of libraries\ncame onto the scenes.",
        "start": 61.72,
        "duration": 1.87
    },
    {
        "text": "They, via CSS and JavaScript,\ngave the appearance",
        "start": 63.59,
        "duration": 3.86
    },
    {
        "text": "that you had a mobile-like\napplication on your phone,",
        "start": 67.45,
        "duration": 2.85
    },
    {
        "text": "but the user interface\nwasn't all that good.",
        "start": 70.3,
        "duration": 2.01
    },
    {
        "text": "And you can tell that this\nisn't really \"native\".",
        "start": 72.31,
        "duration": 2.31
    },
    {
        "text": "That is, code that's in Objective-C or\nSwift on iOS or in Java for Android.",
        "start": 74.62,
        "duration": 5.76
    },
    {
        "text": "And something always felt a bit off.",
        "start": 80.38,
        "duration": 1.67
    },
    {
        "text": "So you could learn any\none of those languages",
        "start": 82.05,
        "duration": 1.93
    },
    {
        "text": "or pick up the various tool kits\nthat exist to write native software.",
        "start": 83.98,
        "duration": 3.63
    },
    {
        "text": "But it's a decent learning curve.",
        "start": 87.61,
        "duration": 1.42
    },
    {
        "text": "And if you're running a\ncompany or writing an app,",
        "start": 89.03,
        "duration": 1.85
    },
    {
        "text": "you have to generally pick and choose.",
        "start": 90.88,
        "duration": 1.47
    },
    {
        "text": "Do I want to target Android?",
        "start": 92.35,
        "duration": 1.2
    },
    {
        "text": "Do I want to do iOS, or do I essentially\nwant to do twice as much work?",
        "start": 93.55,
        "duration": 3.57
    },
    {
        "text": "And so that alone could\nbe a potential hurdle.",
        "start": 97.12,
        "duration": 2.612
    },
    {
        "text": "And then there were\nthese other libraries",
        "start": 99.732,
        "duration": 1.708
    },
    {
        "text": "that allowed you to approximate the\nexperience of writing your code once,",
        "start": 101.44,
        "duration": 4.86
    },
    {
        "text": "and then run it on both platforms.",
        "start": 106.3,
        "duration": 1.78
    },
    {
        "text": "But there, too, you could always\ntell that something wasn't quite",
        "start": 108.08,
        "duration": 3.23
    },
    {
        "text": "natural for the particular device.",
        "start": 111.31,
        "duration": 1.924
    },
    {
        "text": "And then more recently\nhas come onto the scene",
        "start": 113.234,
        "duration": 1.916
    },
    {
        "text": "a number of new frameworks,\nparticularly React Native,",
        "start": 115.15,
        "duration": 3.8
    },
    {
        "text": "an open source framework\npopularized by Facebook",
        "start": 118.95,
        "duration": 2.44
    },
    {
        "text": "that really actually now enables truly\nnative cross-platform developments",
        "start": 121.39,
        "duration": 5.34
    },
    {
        "text": "while using JavaScript to\nrather stitch things together",
        "start": 126.73,
        "duration": 2.65
    },
    {
        "text": "and then leaning on the\nframework to provide you",
        "start": 129.38,
        "duration": 2.0
    },
    {
        "text": "with those truly native user interface\nwidgets and other features that",
        "start": 131.38,
        "duration": 3.36
    },
    {
        "text": "would come to expect from\nthose various languages.",
        "start": 134.74,
        "duration": 2.321
    },
    {
        "text": "So what we'll do over the\ncourse of the semester",
        "start": 137.061,
        "duration": 1.999
    },
    {
        "text": "is really dive in deeply\nto mobile app development,",
        "start": 139.06,
        "duration": 2.58
    },
    {
        "text": "specifically building on top\nof this popular framework.",
        "start": 141.64,
        "duration": 2.58
    },
    {
        "text": "You might have heard of\nReacht Native or React",
        "start": 144.22,
        "duration": 2.294
    },
    {
        "text": "in the context of web browsers, which\nhas been around for some time as well.",
        "start": 146.514,
        "duration": 3.166
    },
    {
        "text": "And to a lot of those paradigms that\nfolks have been using for a few years",
        "start": 149.68,
        "duration": 3.083
    },
    {
        "text": "now on laptops and desktops is now\navailable with additional features",
        "start": 152.763,
        "duration": 3.247
    },
    {
        "text": "in a mobile context, especially.",
        "start": 156.01,
        "duration": 1.77
    },
    {
        "text": "So today we're going to dive in\nquite quickly to JavaScript itself.",
        "start": 157.78,
        "duration": 3.18
    },
    {
        "text": "If you have a bit of background\nin that, that's great.",
        "start": 160.96,
        "duration": 2.25
    },
    {
        "text": "We'll hopefully fill in\nsome gaps along the way.",
        "start": 163.21,
        "duration": 1.8
    },
    {
        "text": "And we'll also look at some of the\nmore advanced features both tonight",
        "start": 165.01,
        "duration": 2.916
    },
    {
        "text": "and next week as well,\nparticularly ES6 6 or ECMAScript 6,",
        "start": 167.926,
        "duration": 3.714
    },
    {
        "text": "which is essentially the\nlatest version of JavaScript,",
        "start": 171.64,
        "duration": 2.42
    },
    {
        "text": "and with it some new syntactic\nfeatures and programmatic capabilities.",
        "start": 174.06,
        "duration": 4.024
    },
    {
        "text": "A week after that, we'll\ntake a look at React itself",
        "start": 178.084,
        "duration": 2.166
    },
    {
        "text": "and JSX, which rather comingles\ncode with XML or a markup language,",
        "start": 180.25,
        "duration": 4.26
    },
    {
        "text": "if you're familiar.",
        "start": 184.51,
        "duration": 1.03
    },
    {
        "text": "And then look at some of\nthe particular features",
        "start": 185.54,
        "duration": 2.42
    },
    {
        "text": "and UI features that you get\nwith a framework like React JS.",
        "start": 187.96,
        "duration": 3.12
    },
    {
        "text": "Components, props, how\nyou deal with states,",
        "start": 191.08,
        "duration": 2.37
    },
    {
        "text": "how you can actually stylize things,\nget user input, and create views,",
        "start": 193.45,
        "duration": 3.81
    },
    {
        "text": "if you're familiar with paradigms\nlike MVC, model view controller.",
        "start": 197.26,
        "duration": 3.68
    },
    {
        "text": "Review governs what it is the user\nis seeing and interacting with.",
        "start": 200.94,
        "duration": 3.13
    },
    {
        "text": "We'll take a look at\ndebugging techniques,",
        "start": 204.07,
        "duration": 1.75
    },
    {
        "text": "particularly for a mobile platform,\nwhich might not necessarily be obvious",
        "start": 205.82,
        "duration": 3.08
    },
    {
        "text": "if the device you're working on is\nhere, and the device you're testing on",
        "start": 208.9,
        "duration": 3.041
    },
    {
        "text": "is here.",
        "start": 211.941,
        "duration": 0.549
    },
    {
        "text": "We'll give you some tools\nand techniques for that.",
        "start": 212.49,
        "duration": 1.98
    },
    {
        "text": "Focusing ultimately on data and\nnavigation, how you can actually",
        "start": 214.47,
        "duration": 2.77
    },
    {
        "text": "get users around in your applications.",
        "start": 217.24,
        "duration": 2.07
    },
    {
        "text": "And then looking at a popular\nthird party tool and framework",
        "start": 219.31,
        "duration": 2.61
    },
    {
        "text": "called Expo, which actually\nmakes it even easier",
        "start": 221.92,
        "duration": 2.42
    },
    {
        "text": "to develop for this\nparticular environment",
        "start": 224.34,
        "duration": 1.75
    },
    {
        "text": "and get started and\nget worked on quickly.",
        "start": 226.09,
        "duration": 1.92
    },
    {
        "text": "Looking at Redux and state\nmanagement again more generally.",
        "start": 228.01,
        "duration": 2.52
    },
    {
        "text": "Performance tuning of your applications.",
        "start": 230.53,
        "duration": 2.094
    },
    {
        "text": "And then finally how you\nactually get this thing off",
        "start": 232.624,
        "duration": 2.166
    },
    {
        "text": "of your laptop or desktop\nand off of just your phone",
        "start": 234.79,
        "duration": 3.21
    },
    {
        "text": "and on to other phones\nand mobile devices.",
        "start": 238.0,
        "duration": 2.547
    },
    {
        "text": "And we'll apply all of\nthese lessons learned",
        "start": 240.547,
        "duration": 1.833
    },
    {
        "text": "and the real challenges, and the\nhands dirty portion of the class",
        "start": 242.38,
        "duration": 2.708
    },
    {
        "text": "will be by way of the course's projects.",
        "start": 245.088,
        "duration": 1.912
    },
    {
        "text": "Three of them assign specifications from\nus that spec out exactly what it is you",
        "start": 247.0,
        "duration": 3.75
    },
    {
        "text": "should aspire to build.",
        "start": 250.75,
        "duration": 1.32
    },
    {
        "text": "And then the class will culminate\nwith the final project, where",
        "start": 252.07,
        "duration": 2.76
    },
    {
        "text": "it will be up to you to propose, to\ndesign, and ultimately implement most",
        "start": 254.83,
        "duration": 5.28
    },
    {
        "text": "any mobile application a top\nReact Native, as you might like.",
        "start": 260.11,
        "duration": 4.38
    },
    {
        "text": "Without further ado, let's dive\ninto an overview of the class itself",
        "start": 264.49,
        "duration": 4.02
    },
    {
        "text": "as well as, then.",
        "start": 268.51,
        "duration": 1.05
    },
    {
        "text": "JavaScript.",
        "start": 269.56,
        "duration": 0.5
    },
    {
        "text": "Let me turn things\nover already to Jordan.",
        "start": 270.06,
        "duration": 1.51
    },
    {
        "text": "JORDAN HAYASHI: Great, yeah.",
        "start": 271.57,
        "duration": 1.166
    },
    {
        "text": "Thanks for the great intro, David.",
        "start": 272.736,
        "duration": 2.104
    },
    {
        "text": "So a few things about\nthe course itself, you",
        "start": 274.84,
        "duration": 4.43
    },
    {
        "text": "can find information on the website.",
        "start": 279.27,
        "duration": 1.5
    },
    {
        "text": "I e-mailed you all the\nlink earlier today.",
        "start": 280.77,
        "duration": 2.8
    },
    {
        "text": "On it, there's a link\nto the Slack, which",
        "start": 283.57,
        "duration": 2.46
    },
    {
        "text": "is what we're going to use for\npretty instant communication.",
        "start": 286.03,
        "duration": 3.182
    },
    {
        "text": "You can create groups\namongst yourselves,",
        "start": 289.212,
        "duration": 1.708
    },
    {
        "text": "and we'll use that for any quick\ntidbits when we have to send out.",
        "start": 290.92,
        "duration": 4.162
    },
    {
        "text": "And then, additionally,\nwe have our staff email",
        "start": 295.082,
        "duration": 1.958
    },
    {
        "text": "that's linked as well, which is how\nyou can just email the staff directly.",
        "start": 297.04,
        "duration": 4.83
    },
    {
        "text": "And so a little bit about lectures.",
        "start": 301.87,
        "duration": 2.13
    },
    {
        "text": "We'll have a short break about halfway.",
        "start": 304.0,
        "duration": 1.625
    },
    {
        "text": "You can get up, you can use the\nbathroom, go rest your legs.",
        "start": 305.625,
        "duration": 4.075
    },
    {
        "text": "If you have a question at\nall during the lecture,",
        "start": 309.7,
        "duration": 2.43
    },
    {
        "text": "feel free to just shoot up your\nhand or interrupt me directly.",
        "start": 312.13,
        "duration": 3.342
    },
    {
        "text": "Concepts constantly build on each\nother, so it's pretty important",
        "start": 315.472,
        "duration": 2.708
    },
    {
        "text": "to learn everything\nup to a certain point",
        "start": 318.18,
        "duration": 2.0
    },
    {
        "text": "in order to build off of it later on.",
        "start": 320.18,
        "duration": 2.702
    },
    {
        "text": "And if something isn't super\nimportant to know when you ask",
        "start": 322.882,
        "duration": 2.458
    },
    {
        "text": "a question about it, I'll let you know.",
        "start": 325.34,
        "duration": 1.624
    },
    {
        "text": "So don't worry about\nasking dumb questions.",
        "start": 326.964,
        "duration": 2.336
    },
    {
        "text": "And the staff will be monitoring\nthe Slack during lecture.",
        "start": 329.3,
        "duration": 3.63
    },
    {
        "text": "So if people online have any\nquestions, feel free to post there,",
        "start": 332.93,
        "duration": 3.15
    },
    {
        "text": "and the staff will interrupt me.",
        "start": 336.08,
        "duration": 2.71
    },
    {
        "text": "Another thing, I love live examples.",
        "start": 338.79,
        "duration": 2.45
    },
    {
        "text": "I think the best examples\nare created on the spot.",
        "start": 341.24,
        "duration": 2.28
    },
    {
        "text": "And with that comes\na little bit of risk.",
        "start": 343.52,
        "duration": 2.83
    },
    {
        "text": "So live coding does have risks.",
        "start": 346.35,
        "duration": 1.43
    },
    {
        "text": "If I make a mistake,\nfeel free to correct me.",
        "start": 347.78,
        "duration": 2.25
    },
    {
        "text": "I have some candy in the lectern.",
        "start": 350.03,
        "duration": 2.392
    },
    {
        "text": "So if you correct me,\nI'll give you some candy.",
        "start": 352.422,
        "duration": 1.958
    },
    {
        "text": "For those online, sorry you don't get\ncandy, but you can have some glory.",
        "start": 354.38,
        "duration": 4.89
    },
    {
        "text": "Cool.",
        "start": 359.27,
        "duration": 1.489
    },
    {
        "text": "Let's start talking about JavaScript.",
        "start": 360.759,
        "duration": 1.541
    },
    {
        "text": "So JavaScript is an\ninterpretive language.",
        "start": 362.3,
        "duration": 2.295
    },
    {
        "text": "So I posted a little\nbit in the Slack earlier",
        "start": 364.595,
        "duration": 1.875
    },
    {
        "text": "asking about most comfortable languages.",
        "start": 366.47,
        "duration": 2.01
    },
    {
        "text": "Most of you guys were\nsaying JavaScript, but I",
        "start": 368.48,
        "duration": 2.49
    },
    {
        "text": "know those of you who took CS50\nmight have some experience with CE,",
        "start": 370.97,
        "duration": 3.87
    },
    {
        "text": "which is a compiled language.",
        "start": 374.84,
        "duration": 2.46
    },
    {
        "text": "So JavaScript is not compiled.",
        "start": 377.3,
        "duration": 2.807
    },
    {
        "text": "It's actually interpreted, so an\ninterpreter will read line by line,",
        "start": 380.107,
        "duration": 2.833
    },
    {
        "text": "execute that code line by line.",
        "start": 382.94,
        "duration": 2.01
    },
    {
        "text": "Each browser has built into\nit its own JavaScript engine,",
        "start": 384.95,
        "duration": 3.935
    },
    {
        "text": "which either interprets the code.",
        "start": 388.885,
        "duration": 1.375
    },
    {
        "text": "It might do some magic with\nsome just-in-time compilation,",
        "start": 390.26,
        "duration": 2.757
    },
    {
        "text": "but for the most part it's just\nreading your code line by line",
        "start": 393.017,
        "duration": 2.583
    },
    {
        "text": "and executing it.",
        "start": 395.6,
        "duration": 1.53
    },
    {
        "text": "Each browser actually has its\nown engine, and there are names.",
        "start": 397.13,
        "duration": 3.09
    },
    {
        "text": "So chrome is called V8.",
        "start": 400.22,
        "duration": 2.37
    },
    {
        "text": "If you've heard of Node.js at all, it\nalso uses that same node v8 engine.",
        "start": 402.59,
        "duration": 4.81
    },
    {
        "text": "Firefox has SpiderMonkey.",
        "start": 407.4,
        "duration": 1.25
    },
    {
        "text": "Safari has JavaScriptCore.",
        "start": 408.65,
        "duration": 1.6
    },
    {
        "text": "Chakra for Microsoft Edge\nand Internet Explorer.",
        "start": 410.25,
        "duration": 2.45
    },
    {
        "text": "You don't really need\nto know these names,",
        "start": 412.7,
        "duration": 1.75
    },
    {
        "text": "but it's a little bit important just\nto know that different ones exist,",
        "start": 414.45,
        "duration": 3.29
    },
    {
        "text": "because JavaScript actually\nis built off of a standard.",
        "start": 417.74,
        "duration": 3.72
    },
    {
        "text": "The standard is put out by ECMA,\nwhich stands for the European Computer",
        "start": 421.46,
        "duration": 3.6
    },
    {
        "text": "Manufacturers Association.",
        "start": 425.06,
        "duration": 1.89
    },
    {
        "text": "And that association is in charge of\njust putting out a spec, meaning hey,",
        "start": 426.95,
        "duration": 6.192
    },
    {
        "text": "I know you guys have this language.",
        "start": 433.142,
        "duration": 1.458
    },
    {
        "text": "But this is exactly what\nthis language needs to do.",
        "start": 434.6,
        "duration": 2.125
    },
    {
        "text": "And for every single\nfunction, this is exactly how",
        "start": 436.725,
        "duration": 2.585
    },
    {
        "text": "this function should behave.",
        "start": 439.31,
        "duration": 1.65
    },
    {
        "text": "So each of these browsers--",
        "start": 440.96,
        "duration": 1.73
    },
    {
        "text": "the engines in the browsers--",
        "start": 442.69,
        "duration": 1.45
    },
    {
        "text": "actually implement the standard.",
        "start": 444.14,
        "duration": 1.99
    },
    {
        "text": "But there are some functions where\nthe standard is a little bit hazy on,",
        "start": 446.13,
        "duration": 3.14
    },
    {
        "text": "or maybe it doesn't even define\nthis particular function.",
        "start": 449.27,
        "duration": 3.37
    },
    {
        "text": "And there's no hard line in exactly\nwhat that function should do.",
        "start": 452.64,
        "duration": 4.7
    },
    {
        "text": "So they may differ for anything\nnot defined by that standard.",
        "start": 457.34,
        "duration": 3.18
    },
    {
        "text": "And some syntax.",
        "start": 463.37,
        "duration": 2.41
    },
    {
        "text": "Let's actually hop into\ncode directly for this.",
        "start": 465.78,
        "duration": 3.81
    },
    {
        "text": "So let's do-- cool.",
        "start": 469.59,
        "duration": 4.35
    },
    {
        "text": "And the way that you declare\nvariables in JavaScript,",
        "start": 473.94,
        "duration": 2.64
    },
    {
        "text": "there's actually three different ways.",
        "start": 476.58,
        "duration": 1.93
    },
    {
        "text": "We'll talk about that\na little more later.",
        "start": 478.51,
        "duration": 1.749
    },
    {
        "text": "But for now, we'll just use\nthis keyword called const.",
        "start": 480.259,
        "duration": 2.402
    },
    {
        "text": "So if I want to declare a\nvariable, I'd say const.",
        "start": 482.661,
        "duration": 2.189
    },
    {
        "text": "So give me a variable called first name.",
        "start": 484.85,
        "duration": 1.76
    },
    {
        "text": "And I can give it any value I want.",
        "start": 491.89,
        "duration": 2.55
    },
    {
        "text": "So let's just call it my first name.",
        "start": 494.44,
        "duration": 1.66
    },
    {
        "text": "So you notice I have a\nstring literal there.",
        "start": 499.4,
        "duration": 1.89
    },
    {
        "text": "It's using double quotes, and then I\nend that statement with a semi-colon.",
        "start": 501.29,
        "duration": 6.24
    },
    {
        "text": "I can also do a last name.",
        "start": 507.53,
        "duration": 1.2
    },
    {
        "text": "And if you notice, this time, I\nstill have that string literal,",
        "start": 513.736,
        "duration": 2.624
    },
    {
        "text": "but this time I'm using single quotes.",
        "start": 516.36,
        "duration": 1.439
    },
    {
        "text": "Because in JavaScript\nthere's really no difference",
        "start": 517.799,
        "duration": 2.083
    },
    {
        "text": "between double and single quotes.",
        "start": 519.882,
        "duration": 1.398
    },
    {
        "text": "You also notice I omitted that\nsemi-colon, which in JavaScript is OK.",
        "start": 521.28,
        "duration": 3.72
    },
    {
        "text": "So my colons are actually optional.",
        "start": 525.0,
        "duration": 1.47
    },
    {
        "text": "So say I wanted something\nthat was not a string.",
        "start": 529.44,
        "duration": 2.88
    },
    {
        "text": "I can just give it a value, like 42.",
        "start": 532.32,
        "duration": 3.63
    },
    {
        "text": "So in C, you might see\nsomething like, give me an int,",
        "start": 535.95,
        "duration": 3.63
    },
    {
        "text": "or give me a string or a char star.",
        "start": 539.58,
        "duration": 4.622
    },
    {
        "text": "You're declaring types\nright away with C,",
        "start": 544.202,
        "duration": 1.708
    },
    {
        "text": "but for something like JavaScript,\nyou actually don't have to do that.",
        "start": 545.91,
        "duration": 4.78
    },
    {
        "text": "We can also do arrays.",
        "start": 550.69,
        "duration": 1.31
    },
    {
        "text": "And we can just declare them in\nline like this, and I can have--",
        "start": 554.654,
        "duration": 2.666
    },
    {
        "text": "So, if you notice, I actually have\nthree different types all in this array.",
        "start": 574.73,
        "duration": 3.72
    },
    {
        "text": "So I have a string, I have a\nnumber, and I have a function.",
        "start": 578.45,
        "duration": 2.825
    },
    {
        "text": "And this is perfectly fine.",
        "start": 581.275,
        "duration": 1.125
    },
    {
        "text": "JavaScript doesn't really care\nwhat you throw in an array.",
        "start": 582.4,
        "duration": 2.416
    },
    {
        "text": "You can have all sorts of\ndifferent variable types.",
        "start": 584.816,
        "duration": 3.184
    },
    {
        "text": "And so say we want to access\nthose things in an array.",
        "start": 588.0,
        "duration": 2.597
    },
    {
        "text": "Anybody care to guess\nexactly how I would do that?",
        "start": 590.597,
        "duration": 2.083
    },
    {
        "text": "So say I want to execute that function.",
        "start": 592.68,
        "duration": 2.32
    },
    {
        "text": "How might I go about doing that?",
        "start": 595.0,
        "duration": 1.62
    },
    {
        "text": "Any guesses?",
        "start": 596.62,
        "duration": 1.54
    },
    {
        "text": "Yeah.",
        "start": 598.16,
        "duration": 1.567
    },
    {
        "text": "Yeah, exactly.",
        "start": 599.727,
        "duration": 0.583
    },
    {
        "text": "The array of two.",
        "start": 600.31,
        "duration": 0.708
    },
    {
        "text": "So if you're familiar with\nother languages, a lot of them",
        "start": 601.018,
        "duration": 2.592
    },
    {
        "text": "have the same syntax for\nindexing into an array.",
        "start": 603.61,
        "duration": 2.57
    },
    {
        "text": "And so since we have three\nthings in this array,",
        "start": 606.18,
        "duration": 2.71
    },
    {
        "text": "we do what's called zero indexing,\nwhereby the first index in that array",
        "start": 608.89,
        "duration": 3.54
    },
    {
        "text": "is called the zeroth index.",
        "start": 612.43,
        "duration": 1.65
    },
    {
        "text": "And then you count from there.",
        "start": 614.08,
        "duration": 1.41
    },
    {
        "text": "So we have zeroth here,\nfirst, and second here.",
        "start": 615.49,
        "duration": 3.22
    },
    {
        "text": "And so say I want to\naccess that function.",
        "start": 618.71,
        "duration": 2.09
    },
    {
        "text": "I just do array 2, and\nI get that function.",
        "start": 620.8,
        "duration": 2.94
    },
    {
        "text": "And say I now wanted to\nexecute that function.",
        "start": 623.74,
        "duration": 2.43
    },
    {
        "text": "I can, say, execute it like that.",
        "start": 626.17,
        "duration": 1.742
    },
    {
        "text": "So this is something that you\nmight see in other languages,",
        "start": 627.912,
        "duration": 2.458
    },
    {
        "text": "but JavaScript you can do it as well.",
        "start": 630.37,
        "duration": 1.86
    },
    {
        "text": "You can just grab that function out of\nthat array and execute it like that.",
        "start": 632.23,
        "duration": 5.66
    },
    {
        "text": "Say I wanted a for loop, and I wanted\nto console log everything in that array.",
        "start": 637.89,
        "duration": 3.25
    },
    {
        "text": "I can do it just almost\nlike C. So I can do for--",
        "start": 641.14,
        "duration": 5.7
    },
    {
        "text": "this time we'll use\nlet for the variable.",
        "start": 646.84,
        "duration": 2.13
    },
    {
        "text": "We'll talk a little\nmore about that later.",
        "start": 648.97,
        "duration": 2.09
    },
    {
        "text": "So I start at zero.",
        "start": 651.06,
        "duration": 1.327
    },
    {
        "text": "Well i is less than the raised length.",
        "start": 652.387,
        "duration": 1.583
    },
    {
        "text": "[TYPING]",
        "start": 653.97,
        "duration": 2.43
    },
    {
        "text": "You might see me--",
        "start": 668.08,
        "duration": 0.9
    },
    {
        "text": "my personal preference is\nto omit the semicolons,",
        "start": 668.98,
        "duration": 2.85
    },
    {
        "text": "but you might read something\nonline that has them.",
        "start": 671.83,
        "duration": 2.46
    },
    {
        "text": "It really doesn't matter all that much.",
        "start": 674.29,
        "duration": 2.12
    },
    {
        "text": "And so this line of code here.",
        "start": 676.41,
        "duration": 1.25
    },
    {
        "text": "You might have seen a for loop in\nother languages that you've used.",
        "start": 677.66,
        "duration": 2.54
    },
    {
        "text": "So this one is just saying\nfor give me a variable that's",
        "start": 680.2,
        "duration": 2.58
    },
    {
        "text": "called i that starts at zero.",
        "start": 682.78,
        "duration": 1.92
    },
    {
        "text": "And while it's less than the\nnumber of values in the array--",
        "start": 684.7,
        "duration": 2.97
    },
    {
        "text": "array.length-- just\nkeep incrementing it.",
        "start": 687.67,
        "duration": 2.13
    },
    {
        "text": "And then every single\ntime console.log, which",
        "start": 689.8,
        "duration": 2.85
    },
    {
        "text": "is JavaScript's print function,\nwhatever that value in that array is.",
        "start": 692.65,
        "duration": 5.07
    },
    {
        "text": "So we can actually run this.",
        "start": 697.72,
        "duration": 1.23
    },
    {
        "text": "And as you see the first\ntime, line 12, where",
        "start": 702.92,
        "duration": 8.36
    },
    {
        "text": "we say index into that array to\nthe second value, and call it.",
        "start": 711.28,
        "duration": 4.74
    },
    {
        "text": "That's what's printing high.",
        "start": 716.02,
        "duration": 1.47
    },
    {
        "text": "And this for loop here will now\nprint string 42 and this thing called",
        "start": 717.49,
        "duration": 3.18
    },
    {
        "text": "function, which is this function.",
        "start": 720.67,
        "duration": 3.23
    },
    {
        "text": "Cool, any questions on syntax?",
        "start": 723.9,
        "duration": 2.32
    },
    {
        "text": "Yeah.",
        "start": 726.22,
        "duration": 0.6
    },
    {
        "text": "AUDIENCE: In your array\nthere, does it matter if you",
        "start": 726.82,
        "duration": 3.08
    },
    {
        "text": "have that third comma after your--",
        "start": 729.9,
        "duration": 1.66
    },
    {
        "text": "JORDAN HAYASHI: It does not matter.",
        "start": 731.56,
        "duration": 1.458
    },
    {
        "text": "So the question was, does it matter on\nline 9 that comment at the very end?",
        "start": 733.018,
        "duration": 4.292
    },
    {
        "text": "And so JavaScript allows you to have\ntrailing commas, meaning in arrays,",
        "start": 737.31,
        "duration": 3.46
    },
    {
        "text": "objects, or even function calls.",
        "start": 740.77,
        "duration": 1.742
    },
    {
        "text": "You can actually have extra commas, and\nit doesn't matter whether you have it",
        "start": 742.512,
        "duration": 3.208
    },
    {
        "text": "or not.",
        "start": 745.72,
        "duration": 0.63
    },
    {
        "text": "It's optional just\nlike the semicolon is.",
        "start": 746.35,
        "duration": 2.37
    },
    {
        "text": "But were I to omit\nthe comma here and try",
        "start": 748.72,
        "duration": 2.94
    },
    {
        "text": "to run that, I'm going to get\na syntax error as expected.",
        "start": 751.66,
        "duration": 4.86
    },
    {
        "text": "Cool, any other questions?",
        "start": 760.2,
        "duration": 3.134
    },
    {
        "text": "Great.",
        "start": 763.334,
        "duration": 1.476
    },
    {
        "text": "So back to slides.",
        "start": 764.81,
        "duration": 0.75
    },
    {
        "text": "So types.",
        "start": 765.56,
        "duration": 0.594
    },
    {
        "text": "So we talked about types\na little bit earlier,",
        "start": 766.154,
        "duration": 1.916
    },
    {
        "text": "and I'm just going to talk a\nlittle bit more about them.",
        "start": 768.07,
        "duration": 2.68
    },
    {
        "text": "So JavaScript has what's called dynamic\ntyping, meaning given a variable,",
        "start": 770.75,
        "duration": 4.13
    },
    {
        "text": "it has no type associated with it.",
        "start": 774.88,
        "duration": 2.05
    },
    {
        "text": "So just like I said, give me\na variable called first name",
        "start": 776.93,
        "duration": 3.59
    },
    {
        "text": "and set it equal to a string.",
        "start": 780.52,
        "duration": 1.92
    },
    {
        "text": "I could actually change\nthat later to, say, a type",
        "start": 782.44,
        "duration": 2.46
    },
    {
        "text": "number or a Boolean\nor anything like that.",
        "start": 784.9,
        "duration": 2.22
    },
    {
        "text": "And JavaScript is fine with that just\nbecause it has those dynamic types.",
        "start": 787.12,
        "duration": 4.17
    },
    {
        "text": "And there a certain\nnumber of primitive types.",
        "start": 791.29,
        "duration": 2.13
    },
    {
        "text": "Primitive types are types that have\nno methods, and they're immutable.",
        "start": 793.42,
        "duration": 4.36
    },
    {
        "text": "And so undefined, null are two of them.",
        "start": 797.78,
        "duration": 2.54
    },
    {
        "text": "Boolean.",
        "start": 800.32,
        "duration": 0.81
    },
    {
        "text": "Everybody should know\nBoolean true or false.",
        "start": 801.13,
        "duration": 2.86
    },
    {
        "text": "Number 1, 2, 3, negative 1, 2, 3.",
        "start": 803.99,
        "duration": 3.55
    },
    {
        "text": "It has no float, so 0 and\n0.1 are both of type number.",
        "start": 807.54,
        "duration": 6.79
    },
    {
        "text": "String, which are the\nthings between the quotes.",
        "start": 814.33,
        "duration": 6.45
    },
    {
        "text": "And then symbol, which is\nsomething that's new in ES6,",
        "start": 820.78,
        "duration": 2.43
    },
    {
        "text": "but we're not going to talk about\nit, nor are we going to use it,",
        "start": 823.21,
        "duration": 5.13
    },
    {
        "text": "and then everything else is an object,\nand we'll talk a little bit more",
        "start": 828.34,
        "duration": 3.382
    },
    {
        "text": "about that later.",
        "start": 831.722,
        "duration": 0.708
    },
    {
        "text": "Cool and so a lot of languages\nhave this thing where",
        "start": 836.24,
        "duration": 5.49
    },
    {
        "text": "you change one type to another type.",
        "start": 841.73,
        "duration": 1.87
    },
    {
        "text": "So since JavaScript\nis dynamically typed,",
        "start": 843.6,
        "duration": 2.18
    },
    {
        "text": "we have this thing called typecasting.",
        "start": 845.78,
        "duration": 3.02
    },
    {
        "text": "So coercion is the act of changing\none type to a different type,",
        "start": 848.8,
        "duration": 3.67
    },
    {
        "text": "and there's two different ways\nyou can coerce these variables.",
        "start": 852.47,
        "duration": 2.88
    },
    {
        "text": "So say, as an example, we\nhave this const called x",
        "start": 855.35,
        "duration": 3.18
    },
    {
        "text": "and we give it a value 42.",
        "start": 858.53,
        "duration": 2.04
    },
    {
        "text": "Say I wanted to change\nthat value to a string.",
        "start": 860.57,
        "duration": 2.22
    },
    {
        "text": "There are a couple\ndifferent ways I can do it.",
        "start": 862.79,
        "duration": 1.24
    },
    {
        "text": "There's explicit coercion.",
        "start": 864.03,
        "duration": 1.76
    },
    {
        "text": "There's implicit coercion.",
        "start": 865.79,
        "duration": 1.3
    },
    {
        "text": "So explicit is, hey, I'm\njust going to tell you",
        "start": 867.09,
        "duration": 2.57
    },
    {
        "text": "exactly what I want by wrapping\nit with the type that I want,",
        "start": 869.66,
        "duration": 4.29
    },
    {
        "text": "and give it to me.",
        "start": 873.95,
        "duration": 1.17
    },
    {
        "text": "And so that's being very\nexplicit with what I want.",
        "start": 875.12,
        "duration": 2.19
    },
    {
        "text": "And so the example of\nthat would be say I",
        "start": 877.31,
        "duration": 1.83
    },
    {
        "text": "want to get a string from that value x.",
        "start": 879.14,
        "duration": 2.22
    },
    {
        "text": "I just wrap it with capital string,\nand it pops out 42 with a string.",
        "start": 881.36,
        "duration": 5.39
    },
    {
        "text": "There's also a way of\ndoing it implicitly,",
        "start": 886.75,
        "duration": 1.75
    },
    {
        "text": "which is I'm going to rely\non the behavior of JavaScript",
        "start": 888.5,
        "duration": 3.24
    },
    {
        "text": "in order to get this to a string.",
        "start": 891.74,
        "duration": 1.69
    },
    {
        "text": "And so say I want to\nadd 42 to empty string.",
        "start": 893.43,
        "duration": 4.859
    },
    {
        "text": "That wouldn't really make sense\nif I wanted to have a number,",
        "start": 898.289,
        "duration": 2.541
    },
    {
        "text": "but since 42 is easily\ncastable to a string,",
        "start": 900.83,
        "duration": 2.49
    },
    {
        "text": "I can say, hey, give me\n42, add an empty string,",
        "start": 903.32,
        "duration": 3.39
    },
    {
        "text": "and I expect to get back\nsomething of type string.",
        "start": 906.71,
        "duration": 2.85
    },
    {
        "text": "That is called implicit coercion.",
        "start": 909.56,
        "duration": 3.61
    },
    {
        "text": "And so how might we go\nabout comparing-- oh, yeah.",
        "start": 913.17,
        "duration": 2.166
    },
    {
        "text": "Question.",
        "start": 915.336,
        "duration": 0.5
    },
    {
        "text": "AUDIENCE: Is the string passing\nbehind the same ex.2 string?",
        "start": 915.836,
        "duration": 3.753
    },
    {
        "text": "JORDAN HAYASHI: Yeah, so another\nway would be to invoke that.",
        "start": 919.589,
        "duration": 2.541
    },
    {
        "text": "So the question was,\nwhat about ex.2 string?",
        "start": 924.92,
        "duration": 3.84
    },
    {
        "text": "And so yes, another way to\nget from a number to a string",
        "start": 928.76,
        "duration": 3.69
    },
    {
        "text": "would be to invoke that method on\nthe string or on the number, sorry.",
        "start": 932.45,
        "duration": 4.99
    },
    {
        "text": "Cool, and so how might we\ngo about comparing values?",
        "start": 937.44,
        "duration": 4.16
    },
    {
        "text": "So in most languages you can compare\nvalues with the double equals,",
        "start": 941.6,
        "duration": 3.39
    },
    {
        "text": "but JavaScript has this\nthing called triple equals.",
        "start": 944.99,
        "duration": 2.761
    },
    {
        "text": "So there are two different\nways of comparing equality.",
        "start": 947.751,
        "duration": 2.249
    },
    {
        "text": "There's double equals and\nthere's triple equals,",
        "start": 950.0,
        "duration": 2.26
    },
    {
        "text": "where double equals will\nactually coerce the types,",
        "start": 952.26,
        "duration": 2.48
    },
    {
        "text": "and triple equals require\nthat the types match.",
        "start": 954.74,
        "duration": 4.05
    },
    {
        "text": "And so let's play with\nthat a little bit.",
        "start": 958.79,
        "duration": 1.905
    },
    {
        "text": "So say I have this value, and I want\nto know exactly what type that is.",
        "start": 966.88,
        "duration": 9.51
    },
    {
        "text": "So there's this operator called typeof\nin JavaScript where I can invoke this.",
        "start": 976.39,
        "duration": 4.62
    },
    {
        "text": "And that will give me the type\nof whatever that variable holds.",
        "start": 988.77,
        "duration": 8.99
    },
    {
        "text": "So if I were to run this code,\nthen it would say number,",
        "start": 997.76,
        "duration": 6.05
    },
    {
        "text": "because that is the type.",
        "start": 1003.81,
        "duration": 1.8
    },
    {
        "text": "So right now in order to\nexecute my JavaScript,",
        "start": 1005.61,
        "duration": 1.98
    },
    {
        "text": "I'm using this thing called node,\nwhich, as mentioned earlier,",
        "start": 1007.59,
        "duration": 3.45
    },
    {
        "text": "is basically a command line runtime for\nJavaScript, which is built off of V8.",
        "start": 1011.04,
        "duration": 5.2
    },
    {
        "text": "Any browser has a console where you\ncan also just type JavaScript directly",
        "start": 1019.74,
        "duration": 3.09
    },
    {
        "text": "in there.",
        "start": 1022.83,
        "duration": 1.05
    },
    {
        "text": "So if I were to open up the tools on\nChrome, which is my browser of choice,",
        "start": 1023.88,
        "duration": 6.969
    },
    {
        "text": "I actually get this, which\nis a JavaScript console built",
        "start": 1030.849,
        "duration": 9.441
    },
    {
        "text": "into all of these browsers.",
        "start": 1040.29,
        "duration": 1.613
    },
    {
        "text": "So if you guys are using Chrome at\nhome, and you want to follow along,",
        "start": 1041.903,
        "duration": 2.916
    },
    {
        "text": "you're welcome to open up\nthe developer tools here.",
        "start": 1044.819,
        "duration": 3.991
    },
    {
        "text": "Go to console, and you have your\nown JavaScript interpreter here.",
        "start": 1048.81,
        "duration": 3.93
    },
    {
        "text": "So say I wanted to do that thing\nwhere I do const x equals 42,",
        "start": 1052.74,
        "duration": 5.944
    },
    {
        "text": "and I wanted to get the\ntype of that variable.",
        "start": 1058.684,
        "duration": 1.916
    },
    {
        "text": "I can just do typeof x, and\nit will output that number.",
        "start": 1060.6,
        "duration": 4.62
    },
    {
        "text": "So there's a little bit of a caveat with\nthis, where this might surprise you.",
        "start": 1072.74,
        "duration": 4.52
    },
    {
        "text": "So who thinks they can\nguess what this will output?",
        "start": 1083.33,
        "duration": 4.24
    },
    {
        "text": "First of all, what should it output?",
        "start": 1087.57,
        "duration": 1.725
    },
    {
        "text": "So if we remember back a few slides, we\ntalked about all the different types.",
        "start": 1092.71,
        "duration": 6.4
    },
    {
        "text": "One of them is undefined,\none of them is null.",
        "start": 1099.11,
        "duration": 2.18
    },
    {
        "text": "And say I want to get typeof null.",
        "start": 1101.29,
        "duration": 6.99
    },
    {
        "text": "So what should it output?",
        "start": 1108.28,
        "duration": 3.191
    },
    {
        "text": "Yes?",
        "start": 1111.471,
        "duration": 0.499
    },
    {
        "text": "AUDIENCE: String.",
        "start": 1111.97,
        "duration": 0.845
    },
    {
        "text": "JORDAN HAYASHI: String,\nwhy would you say string?",
        "start": 1112.815,
        "duration": 2.041
    },
    {
        "text": "AUDIENCE: Because [INAUDIBLE].",
        "start": 1116.902,
        "duration": 1.968
    },
    {
        "text": "JORDAN HAYASHI: That's a good guess.",
        "start": 1124.53,
        "duration": 1.5
    },
    {
        "text": "So basically, the answer was so if you\ncan console log it must be a string.",
        "start": 1126.03,
        "duration": 5.34
    },
    {
        "text": "And while that is correct, most of these\ntypes can actually be cast to string.",
        "start": 1131.37,
        "duration": 8.4
    },
    {
        "text": "So we talked about implicit\nversus explicit coercion.",
        "start": 1139.77,
        "duration": 3.12
    },
    {
        "text": "And the way that console\nlog works is it actually",
        "start": 1142.89,
        "duration": 2.64
    },
    {
        "text": "will turn these values into a\nstring in order to console.log them,",
        "start": 1145.53,
        "duration": 4.68
    },
    {
        "text": "but it doesn't necessarily mean the\ntypeof that value itself is a string.",
        "start": 1150.21,
        "duration": 4.99
    },
    {
        "text": "Yeah?",
        "start": 1155.2,
        "duration": 1.48
    },
    {
        "text": "Yeah, so the null.",
        "start": 1156.68,
        "duration": 2.08
    },
    {
        "text": "So we would expect the typeof null\nto be null, since null is actually",
        "start": 1158.76,
        "duration": 3.57
    },
    {
        "text": "a primitive type.",
        "start": 1162.33,
        "duration": 1.69
    },
    {
        "text": "However, this actually returns object.",
        "start": 1164.02,
        "duration": 4.61
    },
    {
        "text": "So JavaScript does have\nsome strange behaviors.",
        "start": 1168.63,
        "duration": 3.64
    },
    {
        "text": "This is one of them.",
        "start": 1172.27,
        "duration": 2.06
    },
    {
        "text": "And people often ask,\nhey, we're on ES6 now.",
        "start": 1174.33,
        "duration": 3.48
    },
    {
        "text": "There have been six different\nversions of JavaScript.",
        "start": 1177.81,
        "duration": 2.91
    },
    {
        "text": "Why don't you just\nchange this to be null?",
        "start": 1180.72,
        "duration": 4.87
    },
    {
        "text": "And the answer that ECMA gives is,\nwell, the whole internet would break.",
        "start": 1185.59,
        "duration": 4.99
    },
    {
        "text": "And so each new version of\nECMAScript should definitely",
        "start": 1190.58,
        "duration": 4.39
    },
    {
        "text": "be backwards compatible\nwith the previous versions.",
        "start": 1194.97,
        "duration": 2.37
    },
    {
        "text": "Otherwise, say I put\nout a website tomorrow.",
        "start": 1197.34,
        "duration": 3.36
    },
    {
        "text": "If somebody comes down and\nchanges the JavaScript spec,",
        "start": 1200.7,
        "duration": 2.91
    },
    {
        "text": "then my website might break.",
        "start": 1203.61,
        "duration": 1.38
    },
    {
        "text": "And so a lot of websites\nactually rely on this to be true.",
        "start": 1204.99,
        "duration": 4.26
    },
    {
        "text": "And, therefore, if a breaking\nversion of ECMAScript is released,",
        "start": 1209.25,
        "duration": 4.47
    },
    {
        "text": "it might actually just have\nunforeseen consequences.",
        "start": 1213.72,
        "duration": 2.677
    },
    {
        "text": "So this is just one of those\nstrange JavaScript gotchas.",
        "start": 1216.397,
        "duration": 2.333
    },
    {
        "text": "Cool, so another good question would\nbe so when should I use double equals",
        "start": 1223.62,
        "duration": 5.16
    },
    {
        "text": "versus triple equals?",
        "start": 1228.78,
        "duration": 1.96
    },
    {
        "text": "And people generally say you\nshould never use double equals,",
        "start": 1230.74,
        "duration": 4.43
    },
    {
        "text": "because that means you have to know\nexactly how every single thing coerces.",
        "start": 1235.17,
        "duration": 4.719
    },
    {
        "text": "And not only you, but every\nsingle person who reads your code",
        "start": 1239.889,
        "duration": 2.541
    },
    {
        "text": "should know what all\nthese values coerce do.",
        "start": 1242.43,
        "duration": 2.97
    },
    {
        "text": "And some of them might\nbe somewhat surprising.",
        "start": 1245.4,
        "duration": 2.2
    },
    {
        "text": "So we have a chart here that talks\nabout the JavaScript equality table.",
        "start": 1247.6,
        "duration": 4.43
    },
    {
        "text": "For those of you who have the slides\nopened, you can click on that link,",
        "start": 1252.03,
        "duration": 3.01
    },
    {
        "text": "and it will bring you to\nthe repo that has this.",
        "start": 1255.04,
        "duration": 2.24
    },
    {
        "text": "Basically, some of these\nstrings are somewhat strange.",
        "start": 1257.28,
        "duration": 3.18
    },
    {
        "text": "Like how empty array is double\nequals to false, which doesn't really",
        "start": 1260.46,
        "duration": 7.74
    },
    {
        "text": "make a ton of sense.",
        "start": 1268.2,
        "duration": 1.432
    },
    {
        "text": "A lot of these don't\nreally make a ton of sense",
        "start": 1269.632,
        "duration": 1.958
    },
    {
        "text": "and, basically, never use\nthat double equals because it",
        "start": 1271.59,
        "duration": 3.99
    },
    {
        "text": "might have some strange behaviors.",
        "start": 1275.58,
        "duration": 1.955
    },
    {
        "text": "So moving on with coercion.",
        "start": 1281.156,
        "duration": 1.124
    },
    {
        "text": "So we talked about coercing\nthings into other types,",
        "start": 1285.22,
        "duration": 3.65
    },
    {
        "text": "but how about if we're getting to bools?",
        "start": 1288.87,
        "duration": 2.22
    },
    {
        "text": "So JavaScript has these\nthings called falsy values.",
        "start": 1291.09,
        "duration": 3.99
    },
    {
        "text": "Who can name a falsy value?",
        "start": 1295.08,
        "duration": 3.39
    },
    {
        "text": "So falsy value is any value that,\nif cast to bool, becomes false.",
        "start": 1298.47,
        "duration": 6.388
    },
    {
        "text": "AUDIENCE: Two.",
        "start": 1304.858,
        "duration": 0.912
    },
    {
        "text": "JORDAN HAYASHI: Two?",
        "start": 1305.77,
        "duration": 1.41
    },
    {
        "text": "So two is actually truthy.",
        "start": 1307.18,
        "duration": 2.13
    },
    {
        "text": "So every number except for one number\nis truthy, well two numbers actually.",
        "start": 1309.31,
        "duration": 4.2
    },
    {
        "text": "AUDIENCE: Zero.",
        "start": 1313.51,
        "duration": 0.86
    },
    {
        "text": "JORDAN HAYASHI: Zero would\nbe one of them, yeah.",
        "start": 1314.37,
        "duration": 2.93
    },
    {
        "text": "Not a number which is actually a number,\nof type number, is also a falsy value.",
        "start": 1317.3,
        "duration": 6.23
    },
    {
        "text": "Who can name another falsy value?",
        "start": 1323.53,
        "duration": 2.144
    },
    {
        "text": "AUDIENCE: Blank?",
        "start": 1325.674,
        "duration": 0.976
    },
    {
        "text": "JORDAN HAYASHI: Blank what?",
        "start": 1326.65,
        "duration": 0.69
    },
    {
        "text": "AUDIENCE: Or empty.",
        "start": 1327.34,
        "duration": 0.84
    },
    {
        "text": "JORDAN HAYASHI: Empty what?",
        "start": 1328.18,
        "duration": 0.69
    },
    {
        "text": "AUDIENCE: Empty array.",
        "start": 1328.87,
        "duration": 1.282
    },
    {
        "text": "JORDAN HAYASHI: Empty\narray is actually truthy.",
        "start": 1330.152,
        "duration": 1.958
    },
    {
        "text": "False is another one.",
        "start": 1336.02,
        "duration": 2.52
    },
    {
        "text": "Undefined, null.",
        "start": 1338.54,
        "duration": 1.02
    },
    {
        "text": "So those are the five falsy values.",
        "start": 1342.59,
        "duration": 2.73
    },
    {
        "text": "So who can name some truthy values?",
        "start": 1345.32,
        "duration": 1.77
    },
    {
        "text": "Somebody said two, which is a valid one.",
        "start": 1349.78,
        "duration": 2.39
    },
    {
        "text": "Three, four, every other number other\nthan zero, negative zero, not a number.",
        "start": 1352.17,
        "duration": 5.98
    },
    {
        "text": "Empty array is also another truthy.",
        "start": 1358.15,
        "duration": 2.43
    },
    {
        "text": "Empty object and\nliterally everything else.",
        "start": 1360.58,
        "duration": 3.27
    },
    {
        "text": "So anything other than those\nvalues right there are truthy.",
        "start": 1363.85,
        "duration": 3.75
    },
    {
        "text": "Cool, so objects, arrays,\nfunctions, objects.",
        "start": 1371.73,
        "duration": 3.417
    },
    {
        "text": "It looks like I put objects twice\nthere, but I actually put it four times.",
        "start": 1375.147,
        "duration": 3.083
    },
    {
        "text": "So JavaScript has this weird\nthing where if it's not",
        "start": 1378.23,
        "duration": 3.56
    },
    {
        "text": "one of those primitive\nvalues, it's an object.",
        "start": 1381.79,
        "duration": 1.92
    },
    {
        "text": "And so we'll talk about\nthis thing in a little bit",
        "start": 1386.637,
        "duration": 2.083
    },
    {
        "text": "called prototype\ninheritance, which talks",
        "start": 1388.72,
        "duration": 2.37
    },
    {
        "text": "about how these objects\ninherit from each other",
        "start": 1391.09,
        "duration": 2.64
    },
    {
        "text": "and how they actually\nwork under the hood.",
        "start": 1393.73,
        "duration": 1.83
    },
    {
        "text": "But first let's compare those two types.",
        "start": 1395.56,
        "duration": 1.89
    },
    {
        "text": "So we talked about primitives\nearlier, which is--",
        "start": 1397.45,
        "duration": 2.25
    },
    {
        "text": "who can name some of the primitives?",
        "start": 1399.7,
        "duration": 3.525
    },
    {
        "text": "AUDIENCE: Null.",
        "start": 1403.225,
        "duration": 0.895
    },
    {
        "text": "JORDAN HAYASHI: Null, undefined.",
        "start": 1404.12,
        "duration": 3.24
    },
    {
        "text": "AUDIENCE: Number.",
        "start": 1407.36,
        "duration": 0.84
    },
    {
        "text": "JORDAN HAYASHI: Number.",
        "start": 1408.2,
        "duration": 1.394
    },
    {
        "text": "AUDIENCE: Boolean.",
        "start": 1409.594,
        "duration": 0.916
    },
    {
        "text": "JORDAN HAYASHI: Boolean.",
        "start": 1410.51,
        "duration": 0.45
    },
    {
        "text": "AUDIENCE: String.",
        "start": 1410.96,
        "duration": 0.92
    },
    {
        "text": "JORDAN HAYASHI: String.",
        "start": 1411.88,
        "duration": 0.958
    },
    {
        "text": "And simple.",
        "start": 1421.53,
        "duration": 0.737
    },
    {
        "text": "So good, you got them all.",
        "start": 1422.267,
        "duration": 1.083
    },
    {
        "text": "Nice.",
        "start": 1423.35,
        "duration": 0.5
    },
    {
        "text": "So everything other than those\nprimitive types are actually objects.",
        "start": 1428.317,
        "duration": 2.833
    },
    {
        "text": "So primitives are immutable,\nwhich means if you",
        "start": 1431.15,
        "duration": 2.577
    },
    {
        "text": "want to change them, you're actually\nreplacing them with a new value",
        "start": 1433.727,
        "duration": 2.833
    },
    {
        "text": "rather than actually changing them\nthemselves, whereas objects are not.",
        "start": 1436.56,
        "duration": 4.05
    },
    {
        "text": "They're actually mutable.",
        "start": 1440.61,
        "duration": 1.92
    },
    {
        "text": "So who knows what storing\nby reference means?",
        "start": 1442.53,
        "duration": 4.77
    },
    {
        "text": "So storing by reference\nmeans we actually",
        "start": 1447.3,
        "duration": 2.28
    },
    {
        "text": "store a reference to this object\nthing, and we can actually",
        "start": 1449.58,
        "duration": 3.36
    },
    {
        "text": "change what is held there\nwithout actually changing",
        "start": 1452.94,
        "duration": 2.79
    },
    {
        "text": "where that thing is located in memory.",
        "start": 1455.73,
        "duration": 2.55
    },
    {
        "text": "We'll talk a little bit\nmore about that in a second.",
        "start": 1458.28,
        "duration": 4.06
    },
    {
        "text": "But the opposite of that\nwould be storing something",
        "start": 1462.34,
        "duration": 3.23
    },
    {
        "text": "by a value, which is what\nhappens when you have primitives.",
        "start": 1465.57,
        "duration": 2.76
    },
    {
        "text": "So, like I said earlier,\nprimitives are immutable,",
        "start": 1468.33,
        "duration": 2.26
    },
    {
        "text": "which means once you create a\nprimitive, it can't actually be changed.",
        "start": 1470.59,
        "duration": 3.2
    },
    {
        "text": "And when you want to change something,\nyou actually create a new primitive",
        "start": 1473.79,
        "duration": 3.63
    },
    {
        "text": "and replace the old one, whereas\nmutable things are actually",
        "start": 1477.42,
        "duration": 3.51
    },
    {
        "text": "stored by reference, and you\ncan actually change that object.",
        "start": 1480.93,
        "duration": 3.872
    },
    {
        "text": "And so let's play with\nthat a little bit.",
        "start": 1484.802,
        "duration": 1.708
    },
    {
        "text": "So there are a few different\nways to create an object.",
        "start": 1497.68,
        "duration": 2.25
    },
    {
        "text": "One would be this way.",
        "start": 1499.93,
        "duration": 2.06
    },
    {
        "text": "So just saying, give me a new object.",
        "start": 1506.01,
        "duration": 1.77
    },
    {
        "text": "And so now o is this a new object thing.",
        "start": 1510.4,
        "duration": 4.552
    },
    {
        "text": "And say we want to start\npopulating the object.",
        "start": 1514.952,
        "duration": 1.958
    },
    {
        "text": "We can do o.firstname\nand assign that a value.",
        "start": 1516.91,
        "duration": 7.03
    },
    {
        "text": "o.lastname, assign\nthat a different value.",
        "start": 1526.64,
        "duration": 4.424
    },
    {
        "text": "Notice that I have strings with\ndouble quotes and single quotes.",
        "start": 1531.064,
        "duration": 2.666
    },
    {
        "text": "It doesn't matter.",
        "start": 1533.73,
        "duration": 2.526
    },
    {
        "text": "So something other than a string.",
        "start": 1536.256,
        "duration": 1.374
    },
    {
        "text": "We can do a Boolean, so isTeaching.",
        "start": 1537.63,
        "duration": 4.89
    },
    {
        "text": "We can assign that to true.",
        "start": 1542.52,
        "duration": 3.05
    },
    {
        "text": "o.greet, and we can\ngive that a function.",
        "start": 1545.57,
        "duration": 4.255
    },
    {
        "text": "[TYPING]",
        "start": 1549.825,
        "duration": 2.265
    },
    {
        "text": "So that would be one way\nof creating a new object is",
        "start": 1562.904,
        "duration": 2.166
    },
    {
        "text": "to use this new keyword\nalong with capital objects.",
        "start": 1565.07,
        "duration": 2.682
    },
    {
        "text": "And that says, hey,\ngive me a new object.",
        "start": 1567.752,
        "duration": 1.708
    },
    {
        "text": "And I'm just going to fill it up with\nthese values using this dot notation.",
        "start": 1569.46,
        "duration": 3.989
    },
    {
        "text": "Another way to do that would be\nwhat's called an object literal.",
        "start": 1573.449,
        "duration": 2.666
    },
    {
        "text": "So I can just do open\ncurly, close curly, and that",
        "start": 1578.66,
        "duration": 3.63
    },
    {
        "text": "gives me basically a new object.",
        "start": 1582.29,
        "duration": 2.55
    },
    {
        "text": "This is actually the preferred way\nover that old new key word with object,",
        "start": 1584.84,
        "duration": 5.46
    },
    {
        "text": "mostly because a, it's easier\nto read, and well mostly just",
        "start": 1590.3,
        "duration": 3.21
    },
    {
        "text": "because it's easier to read.",
        "start": 1593.51,
        "duration": 2.44
    },
    {
        "text": "And so I can start filling those\nvalues in with o.firstname.",
        "start": 1595.95,
        "duration": 3.075
    },
    {
        "text": "And another way to index into\nthese objects is to do o.lastname.",
        "start": 1603.21,
        "duration": 5.59
    },
    {
        "text": "So notice I use brackets there,\nwhich means inside this bracket,",
        "start": 1611.32,
        "duration": 3.4
    },
    {
        "text": "I'm going to have some\nvalue, and that value",
        "start": 1614.72,
        "duration": 2.03
    },
    {
        "text": "is going to be that key of that object.",
        "start": 1616.75,
        "duration": 1.93
    },
    {
        "text": "So I can do the same thing here.",
        "start": 1618.68,
        "duration": 1.85
    },
    {
        "text": "And say I actually wanted to use not a\nstring literal inside these brackets.",
        "start": 1624.73,
        "duration": 6.63
    },
    {
        "text": "I could also do that.",
        "start": 1631.36,
        "duration": 1.36
    },
    {
        "text": "So I could do isTeaching and do\no and then pass in this variable",
        "start": 1632.72,
        "duration": 11.78
    },
    {
        "text": "here with a value of isTeaching,\nand that will set that key.",
        "start": 1644.5,
        "duration": 7.69
    },
    {
        "text": "And then say I wanted to do o of\ngreet and give that same function.",
        "start": 1655.26,
        "duration": 6.01
    },
    {
        "text": "Call and so those objects\nare basically the same.",
        "start": 1671.07,
        "duration": 4.57
    },
    {
        "text": "And last, we can actually\nput everything in line.",
        "start": 1675.64,
        "duration": 2.26
    },
    {
        "text": "So we can do this.",
        "start": 1677.9,
        "duration": 2.94
    },
    {
        "text": "[TYPING]",
        "start": 1680.84,
        "duration": 1.976
    },
    {
        "text": "Cool, and so those three objects\nare basically the same thing.",
        "start": 1715.47,
        "duration": 3.86
    },
    {
        "text": "It's just three different\nways of declaring objects.",
        "start": 1719.33,
        "duration": 3.93
    },
    {
        "text": "You can also nest objects.",
        "start": 1723.26,
        "duration": 1.22
    },
    {
        "text": "So say I wanted an\nobject within an object.",
        "start": 1724.48,
        "duration": 2.43
    },
    {
        "text": "That's also fine.",
        "start": 1726.91,
        "duration": 3.055
    },
    {
        "text": "Say I wanted to do something like this.",
        "start": 1729.965,
        "duration": 1.625
    },
    {
        "text": "[TYPING]",
        "start": 1731.59,
        "duration": 1.952
    },
    {
        "text": "That's also fine.",
        "start": 1742.83,
        "duration": 0.724
    },
    {
        "text": "So that's an object within an object.",
        "start": 1743.554,
        "duration": 1.541
    },
    {
        "text": "Any questions with that?",
        "start": 1748.1,
        "duration": 1.03
    },
    {
        "text": "Cool.",
        "start": 1752.995,
        "duration": 0.5
    },
    {
        "text": "That's actually--",
        "start": 1756.9,
        "duration": 3.494
    },
    {
        "text": "AUDIENCE: I have a question.",
        "start": 1760.394,
        "duration": 1.166
    },
    {
        "text": "JORDAN: Yeah.",
        "start": 1761.56,
        "duration": 0.798
    },
    {
        "text": "AUDIENCE: Do the elements of the objects\nall have to be labeled with strings?",
        "start": 1762.358,
        "duration": 6.474
    },
    {
        "text": "Like if a key were numbered,\nsay, would that work?",
        "start": 1768.832,
        "duration": 3.984
    },
    {
        "text": "JORDAN: Um, So anything, so anything\nhere, is interpreted as a string.",
        "start": 1772.816,
        "duration": 6.134
    },
    {
        "text": "So say, we were to do, like this,",
        "start": 1778.95,
        "duration": 5.51
    },
    {
        "text": "That would be, basically,\none as a string.",
        "start": 1784.46,
        "duration": 2.59
    },
    {
        "text": "So that, this value here\nwill be cast as a string.",
        "start": 1787.05,
        "duration": 2.5
    },
    {
        "text": "And that's what will be used as the key.",
        "start": 1789.55,
        "duration": 2.51
    },
    {
        "text": "So the question was, can\nwe use numbers, or anything",
        "start": 1792.06,
        "duration": 2.25
    },
    {
        "text": "other than strings as keys in objects?",
        "start": 1794.31,
        "duration": 2.25
    },
    {
        "text": "And the answer is, kind of,\nbecause everything will just",
        "start": 1796.56,
        "duration": 2.82
    },
    {
        "text": "be cast to a string.",
        "start": 1799.38,
        "duration": 1.81
    },
    {
        "text": "Yeah, great question.",
        "start": 1801.19,
        "duration": 1.73
    },
    {
        "text": "Let's actually copy and\npaste this into our browser.",
        "start": 1802.92,
        "duration": 3.982
    },
    {
        "text": "And we confirm that it works.",
        "start": 1806.902,
        "duration": 1.208
    },
    {
        "text": "And so, how might we go about\ngetting those values back out?",
        "start": 1814.24,
        "duration": 3.99
    },
    {
        "text": "So, it's basically the\nsame way we got them in.",
        "start": 1818.23,
        "duration": 2.13
    },
    {
        "text": "So if we do dot, we can see, oh, these\nare all, this is the browser saying,",
        "start": 1820.36,
        "duration": 4.34
    },
    {
        "text": "oh, these are all the\nkeys of the object.",
        "start": 1824.7,
        "duration": 2.05
    },
    {
        "text": "So I can do o3.address, and it\nwill give me back the object.",
        "start": 1826.75,
        "duration": 4.812
    },
    {
        "text": "And say we want to get\nthis number out of here.",
        "start": 1831.562,
        "duration": 1.958
    },
    {
        "text": "How might we do that?",
        "start": 1833.52,
        "duration": 0.875
    },
    {
        "text": "[TYPING]",
        "start": 1834.395,
        "duration": 2.803
    },
    {
        "text": "AUDIENCE: Dot and the number.",
        "start": 1837.198,
        "duration": 1.412
    },
    {
        "text": "JORDAN: Exactly, dot number.",
        "start": 1838.61,
        "duration": 2.79
    },
    {
        "text": "Alternatively, we could\nhave also done this.",
        "start": 1841.4,
        "duration": 1.92
    },
    {
        "text": "[TYPING]",
        "start": 1843.32,
        "duration": 2.34
    },
    {
        "text": "And gotten the same thing.",
        "start": 1845.66,
        "duration": 2.73
    },
    {
        "text": "Any questions with objects?",
        "start": 1848.39,
        "duration": 1.2
    },
    {
        "text": "Yeah.",
        "start": 1852.031,
        "duration": 0.499
    },
    {
        "text": "AUDIENCE: Is there a\nconventional way to do that?",
        "start": 1852.53,
        "duration": 3.325
    },
    {
        "text": "Or is it kind of like reference?",
        "start": 1855.855,
        "duration": 2.604
    },
    {
        "text": "JORDAN: To do what?",
        "start": 1858.459,
        "duration": 0.791
    },
    {
        "text": "AUDIENCE: Just between dot\nnumber and [INAUDIBLE]..",
        "start": 1859.25,
        "duration": 4.248
    },
    {
        "text": "JORDAN: Yes, so the question\nis, is there a conventional way",
        "start": 1865.75,
        "duration": 2.5
    },
    {
        "text": "to get values out of objects?",
        "start": 1868.25,
        "duration": 3.48
    },
    {
        "text": "Generally the convention is\nto use that dot notation.",
        "start": 1871.73,
        "duration": 2.52
    },
    {
        "text": "So say we wanted\no3.address.number, the convention",
        "start": 1874.25,
        "duration": 5.4
    },
    {
        "text": "would be to use the dot\nboth of these times.",
        "start": 1879.65,
        "duration": 2.78
    },
    {
        "text": "But say we didn't know exactly\nwhat we wanted out of it.",
        "start": 1882.43,
        "duration": 3.82
    },
    {
        "text": "We could, so say we had this--",
        "start": 1886.25,
        "duration": 3.25
    },
    {
        "text": "[TYPING]",
        "start": 1889.5,
        "duration": 3.5
    },
    {
        "text": "Something like that, where\nwe have some dynamic key.",
        "start": 1895.994,
        "duration": 2.166
    },
    {
        "text": "Where the key we didn't\nactually know, that's",
        "start": 1898.16,
        "duration": 1.89
    },
    {
        "text": "when you actually have to\nuse the bracket notation.",
        "start": 1900.05,
        "duration": 3.51
    },
    {
        "text": "Where we have o3.address, and\nthen we pass into it that key.",
        "start": 1903.56,
        "duration": 8.13
    },
    {
        "text": "Since key is a dynamic,\nsince it's a variable,",
        "start": 1911.69,
        "duration": 1.93
    },
    {
        "text": "we don't know what it is, we have to\nthen use that bracket notation rather",
        "start": 1913.62,
        "duration": 3.083
    },
    {
        "text": "than the dot.",
        "start": 1916.703,
        "duration": 1.277
    },
    {
        "text": "Great question.",
        "start": 1917.98,
        "duration": 0.96
    },
    {
        "text": "Yeah.",
        "start": 1918.94,
        "duration": 0.681
    },
    {
        "text": "AUDIENCE: Um-- You cannot\ndo 0.1 for example.",
        "start": 1919.621,
        "duration": 3.768
    },
    {
        "text": "[INAUDIBLE]",
        "start": 1923.389,
        "duration": 3.301
    },
    {
        "text": "JORDAN: So, if we did o.1, yeah,\nso, o.1, 1 here, since we're",
        "start": 1926.69,
        "duration": 5.22
    },
    {
        "text": "typing it here, is a number.",
        "start": 1931.91,
        "duration": 2.16
    },
    {
        "text": "And we cannot set keys to numbers.",
        "start": 1934.07,
        "duration": 2.67
    },
    {
        "text": "But if it were an object\nliteral like this,",
        "start": 1936.74,
        "duration": 2.16
    },
    {
        "text": "[TYPING]",
        "start": 1938.9,
        "duration": 2.16
    },
    {
        "text": "JORDAN: It considers this not to\nbe a number, but rather a string.",
        "start": 1941.06,
        "duration": 4.71
    },
    {
        "text": "AUDIENCE: You can the array assignment\nby putting brackets around the one",
        "start": 1945.77,
        "duration": 4.95
    },
    {
        "text": "and passing it as a\nstring, so you can do 0 dot",
        "start": 1950.72,
        "duration": 2.475
    },
    {
        "text": "[TYPING]",
        "start": 1953.195,
        "duration": 1.485
    },
    {
        "text": "AUDIENCE: Our brackets\naround [INAUDIBLE] o",
        "start": 1954.68,
        "duration": 5.692
    },
    {
        "text": "dot open bracket, open\nbraces, and then, quotes, one.",
        "start": 1960.372,
        "duration": 6.683
    },
    {
        "text": "And then set that to a value.",
        "start": 1967.055,
        "duration": 4.005
    },
    {
        "text": "JORDAN: So, I think you mean this?",
        "start": 1971.06,
        "duration": 1.85
    },
    {
        "text": "[TYPING]",
        "start": 1972.91,
        "duration": 5.0
    },
    {
        "text": "Yep.",
        "start": 1977.91,
        "duration": 0.5
    },
    {
        "text": "And I believe you can also do this.",
        "start": 1981.362,
        "duration": 1.458
    },
    {
        "text": "[TYPING]",
        "start": 1982.82,
        "duration": 1.62
    },
    {
        "text": "Because that will get cast to a number.",
        "start": 1984.44,
        "duration": 2.15
    },
    {
        "text": "I mean a string.",
        "start": 1986.59,
        "duration": 2.79
    },
    {
        "text": "Any other questions?",
        "start": 1989.38,
        "duration": 3.415
    },
    {
        "text": "Cool-- yeah?",
        "start": 1992.795,
        "duration": 0.956
    },
    {
        "text": "AUDIENCE: If you have want the number\none inside the bracket notation,",
        "start": 1993.751,
        "duration": 5.757
    },
    {
        "text": "versus the string one\ninside the bracket notation,",
        "start": 1999.508,
        "duration": 3.283
    },
    {
        "text": "it will be treated as the same keys?",
        "start": 2002.791,
        "duration": 1.879
    },
    {
        "text": "JORDAN: Yeah, so the question is, what\nis the difference between this here,",
        "start": 2004.67,
        "duration": 3.79
    },
    {
        "text": "and this here?",
        "start": 2008.46,
        "duration": 1.7
    },
    {
        "text": "The difference is, anything\nbetween the brackets",
        "start": 2010.16,
        "duration": 4.12
    },
    {
        "text": "will get coerced into a string.",
        "start": 2014.28,
        "duration": 1.99
    },
    {
        "text": "And so, since this is already a\nstring, it's just that string one.",
        "start": 2016.27,
        "duration": 3.756
    },
    {
        "text": "Since this is not of\ntype string, it actually",
        "start": 2020.026,
        "duration": 1.874
    },
    {
        "text": "gets implicitly coerced into a string.",
        "start": 2021.9,
        "duration": 3.04
    },
    {
        "text": "And so, like we saw earlier, if\nwe did one plus some empty string,",
        "start": 2024.94,
        "duration": 4.16
    },
    {
        "text": "we get back the string one.",
        "start": 2029.1,
        "duration": 1.59
    },
    {
        "text": "So this becomes a string one,\nand it will index into that.",
        "start": 2030.69,
        "duration": 3.06
    },
    {
        "text": "Whereas, this number\nhere, so if we did o3.1,",
        "start": 2033.75,
        "duration": 3.427
    },
    {
        "text": "[TYPING]",
        "start": 2037.177,
        "duration": 3.663
    },
    {
        "text": "That one does not actually get coerced,\nlike it does between the brackets here.",
        "start": 2040.84,
        "duration": 6.3
    },
    {
        "text": "So JavaScript is basically saying,\nhey, this doesn't really make sense.",
        "start": 2047.14,
        "duration": 3.99
    },
    {
        "text": "I need a string here, not a number.",
        "start": 2051.13,
        "duration": 3.7
    },
    {
        "text": "Cool, any other questions?",
        "start": 2054.83,
        "duration": 1.532
    },
    {
        "text": "Great-- So, let's talk a little\nbit about this thing, where",
        "start": 2063.742,
        "duration": 4.897
    },
    {
        "text": "I was talking about mutating objects.",
        "start": 2068.639,
        "duration": 5.127
    },
    {
        "text": "So say--",
        "start": 2073.766,
        "duration": 0.499
    },
    {
        "text": "[TYPING]",
        "start": 2074.265,
        "duration": 3.225
    },
    {
        "text": "So, say I had this object, so--",
        "start": 2083.38,
        "duration": 2.224
    },
    {
        "text": "In it we had, a gets a, b gets b.",
        "start": 2089.54,
        "duration": 5.28
    },
    {
        "text": "So say I wanted to change\na to be something else?",
        "start": 2097.42,
        "duration": 3.58
    },
    {
        "text": "How might I do that?",
        "start": 2101.0,
        "duration": 1.02
    },
    {
        "text": "Yes.",
        "start": 2105.95,
        "duration": 0.51
    },
    {
        "text": "AUDIENCE: dot a equals--",
        "start": 2106.46,
        "duration": 1.0
    },
    {
        "text": "JORDAN: Yes, so I can update\nthis to be anything else.",
        "start": 2107.46,
        "duration": 2.46
    },
    {
        "text": "[TYPING]",
        "start": 2109.92,
        "duration": 3.24
    },
    {
        "text": "Cool, but say I actually did this.",
        "start": 2113.16,
        "duration": 1.875
    },
    {
        "text": "[TYPING]",
        "start": 2115.035,
        "duration": 2.715
    },
    {
        "text": "Anybody care to guess what\nwould be console logged here?",
        "start": 2128.59,
        "duration": 2.84
    },
    {
        "text": "So basically, what he's doing\nis, we're creating a new object.",
        "start": 2133.99,
        "duration": 2.72
    },
    {
        "text": "And storing it in o.",
        "start": 2136.71,
        "duration": 0.96
    },
    {
        "text": "This object has two keys, a and b, where\ntheir values are a and b respectively.",
        "start": 2137.67,
        "duration": 4.41
    },
    {
        "text": "I'm creating this new object\ncalled o2, and assign a value of o.",
        "start": 2142.08,
        "duration": 5.49
    },
    {
        "text": "I then go reset o.",
        "start": 2147.57,
        "duration": 2.46
    },
    {
        "text": "Not o2 but o.a to be a new value.",
        "start": 2150.03,
        "duration": 2.67
    },
    {
        "text": "And I'm going to console log o2.a.",
        "start": 2152.7,
        "duration": 2.88
    },
    {
        "text": "Anybody care to guess what\nthis is going to console log?",
        "start": 2155.58,
        "duration": 2.59
    },
    {
        "text": "Yeah.",
        "start": 2158.17,
        "duration": 0.5
    },
    {
        "text": "AUDIENCE: a?",
        "start": 2158.67,
        "duration": 1.5
    },
    {
        "text": "JORDAN: So, a guess is a.",
        "start": 2160.17,
        "duration": 1.71
    },
    {
        "text": "What would be the alternative guess?",
        "start": 2161.88,
        "duration": 2.937
    },
    {
        "text": "AUDIENCE: New value.",
        "start": 2164.817,
        "duration": 0.833
    },
    {
        "text": "JORDAN: New value--",
        "start": 2165.65,
        "duration": 2.113
    },
    {
        "text": "[INAUDIBLE]",
        "start": 2167.763,
        "duration": 1.867
    },
    {
        "text": "JORDAN: Yeah, so let's run that.",
        "start": 2169.63,
        "duration": 2.27
    },
    {
        "text": "So you get new value.",
        "start": 2171.9,
        "duration": 0.93
    },
    {
        "text": "And so I talked about this thing\ncalled passing by reference,",
        "start": 2172.83,
        "duration": 2.541
    },
    {
        "text": "and passing by value.",
        "start": 2175.371,
        "duration": 2.659
    },
    {
        "text": "So, basically what's happening\nhere, is that o is being said,",
        "start": 2178.03,
        "duration": 6.08
    },
    {
        "text": "hey, give me a new object, somewhere.",
        "start": 2184.11,
        "duration": 4.14
    },
    {
        "text": "And then store inside of it, a and b.",
        "start": 2188.25,
        "duration": 2.64
    },
    {
        "text": "And then o2 says hey, give me\nanother object and set it to o.",
        "start": 2190.89,
        "duration": 4.11
    },
    {
        "text": "And rather then creating a new\nobject, with the same keys and values,",
        "start": 2195.0,
        "duration": 3.33
    },
    {
        "text": "it's actually pointing\nto that same object.",
        "start": 2198.33,
        "duration": 2.279
    },
    {
        "text": "So this is a case where\nthings are getting stored",
        "start": 2200.609,
        "duration": 2.041
    },
    {
        "text": "by reference, rather than by value.",
        "start": 2202.65,
        "duration": 2.15
    },
    {
        "text": "Meaning, so in CS50, we talked\na little bit about pointers,",
        "start": 2204.8,
        "duration": 3.22
    },
    {
        "text": "and this is the exact same concept.",
        "start": 2208.02,
        "duration": 2.37
    },
    {
        "text": "Where these objects are not stored\nas entire serialized objects,",
        "start": 2210.39,
        "duration": 4.96
    },
    {
        "text": "but rather as references\nto these objects in memory.",
        "start": 2215.35,
        "duration": 3.53
    },
    {
        "text": "So o and o2 are both referencing\nthat same exact object.",
        "start": 2218.88,
        "duration": 3.7
    },
    {
        "text": "So when we go back and say,\nhey update o.a to be new value,",
        "start": 2222.58,
        "duration": 4.71
    },
    {
        "text": "it's changing this\nobject here, and still",
        "start": 2227.29,
        "duration": 2.06
    },
    {
        "text": "o and o2 are both pointing\nto that same object.",
        "start": 2229.35,
        "duration": 3.43
    },
    {
        "text": "So if I were to have updated 02\nhere, and console logged o.a,",
        "start": 2232.78,
        "duration": 6.74
    },
    {
        "text": "we would get that same result. Because o\nand o2 are still both referring to that",
        "start": 2239.52,
        "duration": 4.26
    },
    {
        "text": "same object in memory, and we're\nstill updating that object here.",
        "start": 2243.78,
        "duration": 3.97
    },
    {
        "text": "Does that make sense?",
        "start": 2247.75,
        "duration": 2.65
    },
    {
        "text": "Yeah.",
        "start": 2250.4,
        "duration": 0.61
    },
    {
        "text": "AUDIENCE: So what if you\nwanted them to be different.",
        "start": 2251.01,
        "duration": 2.208
    },
    {
        "text": "Like, what if you wanted them\nto not point to the same thing?",
        "start": 2253.218,
        "duration": 2.662
    },
    {
        "text": "JORDAN: Yeah, so the\nquestion is, what if we",
        "start": 2255.88,
        "duration": 1.95
    },
    {
        "text": "wanted them to have the same\nvalue but be different references?",
        "start": 2257.83,
        "duration": 3.18
    },
    {
        "text": "How might we do that?",
        "start": 2261.01,
        "duration": 1.26
    },
    {
        "text": "There are two different ways.",
        "start": 2262.27,
        "duration": 2.14
    },
    {
        "text": "One, the more annoying way, would just\nbe to type the whole thing out again.",
        "start": 2264.41,
        "duration": 4.58
    },
    {
        "text": "[TYPING]",
        "start": 2268.99,
        "duration": 2.916
    },
    {
        "text": "So now we're guaranteed\nthat o and o2 are",
        "start": 2274.002,
        "duration": 1.708
    },
    {
        "text": "going to be different references to\nan object that is basically the same.",
        "start": 2275.71,
        "duration": 6.42
    },
    {
        "text": "And another way would be --",
        "start": 2282.13,
        "duration": 1.6
    },
    {
        "text": "there are multiple\ndifferent ways to do this.",
        "start": 2283.73,
        "duration": 2.25
    },
    {
        "text": "The most common way in pure\nJavaScript, would be to do this--",
        "start": 2285.98,
        "duration": 3.59
    },
    {
        "text": "[TYPING]",
        "start": 2289.57,
        "duration": 3.486
    },
    {
        "text": "Whereby, object assigned is\nbasically saying, hey, pass in to me",
        "start": 2297.54,
        "duration": 4.315
    },
    {
        "text": "a bunch of arguments.",
        "start": 2301.855,
        "duration": 0.875
    },
    {
        "text": "And every single argument, I'm going\nto merge into the previous one,",
        "start": 2302.73,
        "duration": 3.33
    },
    {
        "text": "those lose keys and values.",
        "start": 2306.06,
        "duration": 1.7
    },
    {
        "text": "And so this is saying,\ngive me a brand new object.",
        "start": 2307.76,
        "duration": 3.14
    },
    {
        "text": "So I'm using the object literal\nhere to mean a new object.",
        "start": 2310.9,
        "duration": 3.05
    },
    {
        "text": "And then merge into it, of the keys\nand values of this object called o.",
        "start": 2313.95,
        "duration": 4.4
    },
    {
        "text": "And so this is basically\nsaying, give me new object,",
        "start": 2318.35,
        "duration": 3.08
    },
    {
        "text": "and then set all of the keys\nand values of o to be in there.",
        "start": 2321.43,
        "duration": 3.92
    },
    {
        "text": "So this is the way of cloning an object.",
        "start": 2325.35,
        "duration": 3.6
    },
    {
        "text": "But say we actually did this",
        "start": 2328.95,
        "duration": 1.31
    },
    {
        "text": "[TYPING]",
        "start": 2330.26,
        "duration": 3.486
    },
    {
        "text": "So, what do we expect\nthis to now print out?",
        "start": 2369.17,
        "duration": 1.9
    },
    {
        "text": "So, we mentioned that line nine,\nwe're taking the keys and values of o,",
        "start": 2374.31,
        "duration": 7.38
    },
    {
        "text": "and merging those into a new object.",
        "start": 2381.69,
        "duration": 4.2
    },
    {
        "text": "And then that line 11 we're\ntaking o2, getting the dot object,",
        "start": 2385.89,
        "duration": 3.93
    },
    {
        "text": "so accessing the value\nwith the key called object.",
        "start": 2389.82,
        "duration": 2.94
    },
    {
        "text": "And then setting that object's\nkey called key to new value.",
        "start": 2392.76,
        "duration": 4.47
    },
    {
        "text": "And then now console\nlogging o to object dot key.",
        "start": 2397.23,
        "duration": 4.1
    },
    {
        "text": "Yeah.",
        "start": 2401.33,
        "duration": 1.44
    },
    {
        "text": "AUDIENCE: So, new value?",
        "start": 2402.77,
        "duration": 2.81
    },
    {
        "text": "JORDAN: Yes, so this, so\nthe guess is new value,",
        "start": 2405.58,
        "duration": 2.0
    },
    {
        "text": "and that is absolutely correct.",
        "start": 2407.58,
        "duration": 2.79
    },
    {
        "text": "So this, so-- line nine here is\ndoing what's called a shallow copy.",
        "start": 2410.37,
        "duration": 4.62
    },
    {
        "text": "Which is just grabbing the\nkeys and values of some object,",
        "start": 2414.99,
        "duration": 3.09
    },
    {
        "text": "and just setting those blindly\ninto some other object.",
        "start": 2418.08,
        "duration": 3.33
    },
    {
        "text": "As opposed to what would\nbe called a deep copy.",
        "start": 2421.41,
        "duration": 3.24
    },
    {
        "text": "Where that would take\nthe keys and values.",
        "start": 2424.65,
        "duration": 2.822
    },
    {
        "text": "And then if the values\nare objects, you'd",
        "start": 2427.472,
        "duration": 1.708
    },
    {
        "text": "also take those objects keys and values.",
        "start": 2429.18,
        "duration": 1.666
    },
    {
        "text": "Do that recursively, and basically\nget every single layer deep cloned.",
        "start": 2430.846,
        "duration": 5.234
    },
    {
        "text": "But since object assigned just\ntakes the keys and values dumbly,",
        "start": 2436.08,
        "duration": 4.23
    },
    {
        "text": "if we have an object in there,\nupdate that object's key.",
        "start": 2440.31,
        "duration": 5.34
    },
    {
        "text": "o.obj and o2.obj are still referencing\nthat same object in memory,",
        "start": 2445.65,
        "duration": 4.38
    },
    {
        "text": "so since we updated--",
        "start": 2450.03,
        "duration": 1.23
    },
    {
        "text": "we mutated that object, it\nwould update in both o2 and o.",
        "start": 2451.26,
        "duration": 5.13
    },
    {
        "text": "Does that makes sense?",
        "start": 2456.39,
        "duration": 3.385
    },
    {
        "text": "Great, any questions about this?",
        "start": 2459.775,
        "duration": 3.495
    },
    {
        "text": "Yeah.",
        "start": 2463.27,
        "duration": 0.5
    },
    {
        "text": "AUDIENCE: How would you do a deep copy?",
        "start": 2463.77,
        "duration": 1.74
    },
    {
        "text": "JORDAN: So, how would you do deep copy?",
        "start": 2465.51,
        "duration": 2.16
    },
    {
        "text": "That's a great question.",
        "start": 2467.67,
        "duration": 1.0
    },
    {
        "text": "There are multiple different ways.",
        "start": 2468.67,
        "duration": 2.91
    },
    {
        "text": "So most people would say use a library.",
        "start": 2471.58,
        "duration": 3.32
    },
    {
        "text": "Meaning, rather than implementing\nthis thing on your own,",
        "start": 2474.9,
        "duration": 2.85
    },
    {
        "text": "just take somebody\nelse's implementation.",
        "start": 2477.75,
        "duration": 3.63
    },
    {
        "text": "But lets, let's actually do that.",
        "start": 2481.38,
        "duration": 1.56
    },
    {
        "text": "That's a good question.",
        "start": 2482.94,
        "duration": 1.06
    },
    {
        "text": "So, how would we do a deep copy?",
        "start": 2484.0,
        "duration": 2.116
    },
    {
        "text": "[TYPING]",
        "start": 2486.116,
        "duration": 3.332
    },
    {
        "text": "So, I know we haven't talked\na ton about JavaScript yet,",
        "start": 2490.88,
        "duration": 3.0
    },
    {
        "text": "but lets actually tried\nto do this together.",
        "start": 2493.88,
        "duration": 2.35
    },
    {
        "text": "So, let's call a function, deep copy.",
        "start": 2496.23,
        "duration": 4.217
    },
    {
        "text": "And we're going to pass\ninto it some object.",
        "start": 2500.447,
        "duration": 1.833
    },
    {
        "text": "And how would we implement\nthis, if we're guaranteed",
        "start": 2506.17,
        "duration": 3.1
    },
    {
        "text": "that no objects have values of objects?",
        "start": 2509.27,
        "duration": 4.5
    },
    {
        "text": "Meaning we are guaranteed not\nto have objects within objects.",
        "start": 2513.77,
        "duration": 4.435
    },
    {
        "text": "How might we do this?",
        "start": 2518.205,
        "duration": 0.875
    },
    {
        "text": "AUDIENCE: Check for the type of the key.",
        "start": 2519.08,
        "duration": 2.42
    },
    {
        "text": "JORDAN: Yes, so we can check\nfor the type of every key.",
        "start": 2521.5,
        "duration": 2.291
    },
    {
        "text": "But if we're guaranteed that no\nvalues are going to be objects,",
        "start": 2523.791,
        "duration": 2.939
    },
    {
        "text": "we can just do a shallow copy right?",
        "start": 2526.73,
        "duration": 3.81
    },
    {
        "text": "Yeah.",
        "start": 2530.54,
        "duration": 1.631
    },
    {
        "text": "AUDIENCE: So check every value?",
        "start": 2532.171,
        "duration": 1.491
    },
    {
        "text": "And if it's, the value is [INAUDIBLE]\nwe have to recursively deep copy that.",
        "start": 2533.662,
        "duration": 5.478
    },
    {
        "text": "JORDAN: Yeah.",
        "start": 2539.14,
        "duration": 0.58
    },
    {
        "text": "So hold that thought.",
        "start": 2539.72,
        "duration": 0.874
    },
    {
        "text": "Let's actually implement\nthis as if we know that there",
        "start": 2540.594,
        "duration": 3.596
    },
    {
        "text": "are no objects inside of objects.",
        "start": 2544.19,
        "duration": 2.14
    },
    {
        "text": "So if that were true, we could\njust return the shallow copy right?",
        "start": 2546.33,
        "duration": 3.22
    },
    {
        "text": "So object.assign",
        "start": 2549.55,
        "duration": 2.515
    },
    {
        "text": "[TYPING]",
        "start": 2552.065,
        "duration": 3.123
    },
    {
        "text": "So this would be a perfectly\nvalid implementation,",
        "start": 2557.527,
        "duration": 2.083
    },
    {
        "text": "if we knew that there's no such\nthing as objects within objects.",
        "start": 2559.61,
        "duration": 4.08
    },
    {
        "text": "But since there are, we're going\nto have to do some magic here.",
        "start": 2563.69,
        "duration": 4.66
    },
    {
        "text": "So, can you repeat your\nrecommendation again?",
        "start": 2568.35,
        "duration": 4.116
    },
    {
        "text": "AUDIENCE: So, check if the--",
        "start": 2572.466,
        "duration": 3.992
    },
    {
        "text": "any of the values is an object.",
        "start": 2576.458,
        "duration": 3.992
    },
    {
        "text": "Then you can't just take\nthat value into a new object,",
        "start": 2580.45,
        "duration": 5.489
    },
    {
        "text": "just to reference the same object,\nwe need to deep copy that object,",
        "start": 2585.939,
        "duration": 7.984
    },
    {
        "text": "instead of just taking [INAUDIBLE].",
        "start": 2593.923,
        "duration": 3.992
    },
    {
        "text": "JORDAN: So basically, so\ncheck every single value,",
        "start": 2612.96,
        "duration": 3.537
    },
    {
        "text": "and see if it's an object.",
        "start": 2616.497,
        "duration": 1.083
    },
    {
        "text": "If it is an object, then go\nahead and deep copy that object.",
        "start": 2617.58,
        "duration": 3.3
    },
    {
        "text": "Otherwise, return that value.",
        "start": 2620.88,
        "duration": 3.206
    },
    {
        "text": "Cool.",
        "start": 2624.086,
        "duration": 1.316
    },
    {
        "text": "So let's do that.",
        "start": 2625.402,
        "duration": 0.708
    },
    {
        "text": "So-- the way to get the keys of\nan object, is this function called",
        "start": 2626.11,
        "duration": 6.65
    },
    {
        "text": "object.keys",
        "start": 2632.76,
        "duration": 1.11
    },
    {
        "text": "[TYPING]",
        "start": 2633.87,
        "duration": 3.318
    },
    {
        "text": "So, so by doing object.keys\nand passing in the object,",
        "start": 2641.46,
        "duration": 3.39
    },
    {
        "text": "we now have an array full of the string\nvalues of the keys in that object.",
        "start": 2644.85,
        "duration": 5.68
    },
    {
        "text": "And so what we're going to do is, we're\ngoing to iterate through those keys.",
        "start": 2650.53,
        "duration": 3.39
    },
    {
        "text": "Check to see if the\nvalue is of an object.",
        "start": 2653.92,
        "duration": 3.29
    },
    {
        "text": "If so, we'll go ahead and clone that.",
        "start": 2657.21,
        "duration": 2.01
    },
    {
        "text": "Let's not worry about functions, or\nany of those other things for now.",
        "start": 2659.22,
        "duration": 3.96
    },
    {
        "text": "Otherwise, just return that value.",
        "start": 2663.18,
        "duration": 3.61
    },
    {
        "text": "So, let's have this for loop--",
        "start": 2666.79,
        "duration": 1.25
    },
    {
        "text": "[TYPING]",
        "start": 2668.04,
        "duration": 3.479
    },
    {
        "text": "And do that.",
        "start": 2680.47,
        "duration": 0.52
    },
    {
        "text": "So first, let's define--",
        "start": 2680.99,
        "duration": 1.49
    },
    {
        "text": "[TYPING]",
        "start": 2682.48,
        "duration": 3.246
    },
    {
        "text": "The new objects that\nwe're going to return.",
        "start": 2689.449,
        "duration": 1.791
    },
    {
        "text": "And let's just start with\nan empty object for now.",
        "start": 2691.24,
        "duration": 4.18
    },
    {
        "text": "And so, now we have to check to see\nif each of these values is an object.",
        "start": 2695.42,
        "duration": 4.07
    },
    {
        "text": "If so, copy it, otherwise return.",
        "start": 2699.49,
        "duration": 2.11
    },
    {
        "text": "So how are we going to check\nthe type of a particular key?",
        "start": 2701.6,
        "duration": 5.345
    },
    {
        "text": "AUDIENCE: Type of operator.",
        "start": 2706.945,
        "duration": 1.125
    },
    {
        "text": "JORDAN: Yeah, exactly,\nthat type of operator.",
        "start": 2708.07,
        "duration": 1.875
    },
    {
        "text": "So we can do if the type of\nobj, and then pass in by keys.",
        "start": 2709.945,
        "duration": 6.877
    },
    {
        "text": "[TYPING]",
        "start": 2716.822,
        "duration": 2.892
    },
    {
        "text": "So what do we want to check against?",
        "start": 2724.331,
        "duration": 1.499
    },
    {
        "text": "[TYPING]",
        "start": 2725.83,
        "duration": 3.199
    },
    {
        "text": "All right, what am I doing wrong here?",
        "start": 2730.4,
        "duration": 2.122
    },
    {
        "text": "AUDIENCE: Three equals.",
        "start": 2732.522,
        "duration": 1.608
    },
    {
        "text": "JORDAN: Yeah, we should always\nuse that three equal signs.",
        "start": 2734.13,
        "duration": 1.53
    },
    {
        "text": "In this case it would matter.",
        "start": 2735.66,
        "duration": 1.208
    },
    {
        "text": "But, we should just get in\nthe habit of doing that.",
        "start": 2736.868,
        "duration": 2.512
    },
    {
        "text": "I mean so if you notice here, we\nactually have bracket notation",
        "start": 2739.38,
        "duration": 3.09
    },
    {
        "text": "within bracket notation.",
        "start": 2742.47,
        "duration": 1.08
    },
    {
        "text": "That is totally fine.",
        "start": 2743.55,
        "duration": 2.361
    },
    {
        "text": "Cool.",
        "start": 2745.911,
        "duration": 0.499
    },
    {
        "text": "So, if something is an object\nto what are we going to turn?",
        "start": 2746.41,
        "duration": 3.5
    },
    {
        "text": "We can do object, new\nobject with that key.",
        "start": 2749.91,
        "duration": 6.59
    },
    {
        "text": "[TYPING]",
        "start": 2756.5,
        "duration": 3.458
    },
    {
        "text": "Equals-- what?",
        "start": 2766.39,
        "duration": 1.48
    },
    {
        "text": "AUDIENCE: The value?",
        "start": 2774.11,
        "duration": 1.44
    },
    {
        "text": "Oh no, I'm sorry, deep copy.",
        "start": 2775.55,
        "duration": 1.45
    },
    {
        "text": "JORDAN: Yeah, let's actually\ndeep copy that value to two.",
        "start": 2777.0,
        "duration": 2.374
    },
    {
        "text": "[TYPING]",
        "start": 2779.374,
        "duration": 3.206
    },
    {
        "text": "Otherwise--",
        "start": 2787.421,
        "duration": 0.499
    },
    {
        "text": "[TYPING]",
        "start": 2787.92,
        "duration": 3.19
    },
    {
        "text": "We can just set it\nequal to the other key.",
        "start": 2793.01,
        "duration": 2.472
    },
    {
        "text": "[TYPING]",
        "start": 2795.482,
        "duration": 3.297
    },
    {
        "text": "And then at the very end, we\ncan just return that new object.",
        "start": 2801.61,
        "duration": 3.44
    },
    {
        "text": "[TYPING]",
        "start": 2805.05,
        "duration": 3.283
    },
    {
        "text": "Cool.",
        "start": 2812.56,
        "duration": 1.66
    },
    {
        "text": "Anybody see any bugs?",
        "start": 2814.22,
        "duration": 2.29
    },
    {
        "text": "Candy opportunity.",
        "start": 2816.51,
        "duration": 2.516
    },
    {
        "text": "All right, let's just\ngo ahead and test this.",
        "start": 2819.026,
        "duration": 3.714
    },
    {
        "text": "So-- let's do--",
        "start": 2822.74,
        "duration": 4.26
    },
    {
        "text": "Do copy o--",
        "start": 2833.776,
        "duration": 0.934
    },
    {
        "text": "Then update o--",
        "start": 2838.646,
        "duration": 2.46
    },
    {
        "text": "[TYPING]",
        "start": 2841.106,
        "duration": 3.444
    },
    {
        "text": "o.obj.key Let's say of to new key.",
        "start": 2846.03,
        "duration": 4.36
    },
    {
        "text": "[TYPING]",
        "start": 2850.39,
        "duration": 3.43
    },
    {
        "text": "o3.obj.key.",
        "start": 2856.76,
        "duration": 0.98
    },
    {
        "text": "Get rid of that.",
        "start": 2863.82,
        "duration": 0.75
    },
    {
        "text": "All right, so moment of truth--",
        "start": 2868.38,
        "duration": 2.163
    },
    {
        "text": "[TYPING]",
        "start": 2870.543,
        "duration": 3.247
    },
    {
        "text": "Key, rather than new key.",
        "start": 2873.79,
        "duration": 1.06
    },
    {
        "text": "So we did it.",
        "start": 2874.85,
        "duration": 2.675
    },
    {
        "text": "Whew.",
        "start": 2877.525,
        "duration": 1.875
    },
    {
        "text": "All right, any other questions about--",
        "start": 2879.4,
        "duration": 1.86
    },
    {
        "text": "objects, mutating,\nreferences, any of that stuff?",
        "start": 2883.9,
        "duration": 2.97
    },
    {
        "text": "No, great.",
        "start": 2890.55,
        "duration": 1.03
    },
    {
        "text": "So, arrays as well, are\nalso stored by reference.",
        "start": 2891.58,
        "duration": 4.3
    },
    {
        "text": "So if we were to do\nthe same exact example,",
        "start": 2895.88,
        "duration": 2.01
    },
    {
        "text": "and rather than updating the\nobject, we updated that array,",
        "start": 2897.89,
        "duration": 4.054
    },
    {
        "text": "we'd end up with the same exact results.",
        "start": 2901.944,
        "duration": 1.666
    },
    {
        "text": "And so, if we were to update our\ndeep copy function to also take",
        "start": 2903.61,
        "duration": 5.58
    },
    {
        "text": "care of arrays, all we have to\ndo is also check, rather than",
        "start": 2909.19,
        "duration": 3.761
    },
    {
        "text": "checking object, also check against\narrays or any other data types",
        "start": 2912.951,
        "duration": 2.749
    },
    {
        "text": "that we're going to check.",
        "start": 2915.7,
        "duration": 1.083
    },
    {
        "text": "Let's move on to prototype inheritance.",
        "start": 2920.5,
        "duration": 3.57
    },
    {
        "text": "So what exactly is\nprototype inheritance?",
        "start": 2924.07,
        "duration": 1.96
    },
    {
        "text": "Well, so non-primitive types\nhave a few properties and methods",
        "start": 2926.03,
        "duration": 3.26
    },
    {
        "text": "associated with them.",
        "start": 2929.29,
        "duration": 1.68
    },
    {
        "text": "So, array, we have this\nthing called array.push,",
        "start": 2930.97,
        "duration": 2.58
    },
    {
        "text": "which will add values to an array.",
        "start": 2933.55,
        "duration": 1.54
    },
    {
        "text": "So, say we have something like--",
        "start": 2935.09,
        "duration": 2.076
    },
    {
        "text": "[TYPING]",
        "start": 2937.166,
        "duration": 2.294
    },
    {
        "text": "An empty array, if we did array.push--",
        "start": 2939.46,
        "duration": 2.73
    },
    {
        "text": "some value, then array\nnow has something in it.",
        "start": 2942.19,
        "duration": 5.631
    },
    {
        "text": "If we were to push\nanother value into it--",
        "start": 2947.821,
        "duration": 1.749
    },
    {
        "text": "It now has two values in it.",
        "start": 2952.435,
        "duration": 1.315
    },
    {
        "text": "So array.prototype.push\nis a method that we",
        "start": 2953.75,
        "duration": 3.77
    },
    {
        "text": "have available on all arrays, that\njust adds new values to an array.",
        "start": 2957.52,
        "duration": 4.96
    },
    {
        "text": "Another one would be like,\nstring.prototype.toUpperCase.",
        "start": 2962.48,
        "duration": 3.175
    },
    {
        "text": "So, say we were to\nhave some string, so--",
        "start": 2965.655,
        "duration": 2.545
    },
    {
        "text": "[TYPING]",
        "start": 2968.2,
        "duration": 2.591
    },
    {
        "text": "If you do str.toUpperCase--",
        "start": 2971.29,
        "duration": 3.86
    },
    {
        "text": "Now we, we're left with a new\nstring with all uppercase.",
        "start": 2975.15,
        "duration": 3.45
    },
    {
        "text": "So, these are just functions that we\ncan invoke on any non-primitive that",
        "start": 2978.6,
        "duration": 4.31
    },
    {
        "text": "gives us something else.",
        "start": 2982.91,
        "duration": 2.64
    },
    {
        "text": "That is available to all\nnon-primitives of a given type.",
        "start": 2985.55,
        "duration": 5.13
    },
    {
        "text": "So each object stores a\nreference to its prototype.",
        "start": 2990.68,
        "duration": 2.49
    },
    {
        "text": "Meaning, it has all the-- it\nknows about all of these methods.",
        "start": 2993.17,
        "duration": 4.38
    },
    {
        "text": "And it stores a reference to the object\nin order to know where these methods--",
        "start": 2997.55,
        "duration": 6.51
    },
    {
        "text": "the code to actually the run that lies.",
        "start": 3004.06,
        "duration": 4.41
    },
    {
        "text": "And say we have a\nprototype chain where there",
        "start": 3008.47,
        "duration": 3.78
    },
    {
        "text": "are a bunch of different\nmethods of the same name.",
        "start": 3012.25,
        "duration": 2.46
    },
    {
        "text": "Whichever one is bound most tightly\nto the instance has the priority.",
        "start": 3014.71,
        "duration": 4.3
    },
    {
        "text": "So say we have an object in\nan array, where array is the--",
        "start": 3019.01,
        "duration": 9.68
    },
    {
        "text": "So say we have a value that is of\ntype array, up the prototype chain",
        "start": 3028.69,
        "duration": 3.3
    },
    {
        "text": "we have arrays, its prototype is\narray, that prototype is object.",
        "start": 3031.99,
        "duration": 4.96
    },
    {
        "text": "Say we have the same named\nmethod on both of these.",
        "start": 3036.95,
        "duration": 2.717
    },
    {
        "text": "If we call that method, the one\nthat's bound most tightly the,",
        "start": 3039.667,
        "duration": 2.583
    },
    {
        "text": "array will take priority.",
        "start": 3042.25,
        "duration": 2.08
    },
    {
        "text": "So let's actually show that.",
        "start": 3044.33,
        "duration": 1.25
    },
    {
        "text": "So, say we have something like--",
        "start": 3045.58,
        "duration": 2.64
    },
    {
        "text": "So array, it has a\nreference to its prototypes.",
        "start": 3052.69,
        "duration": 4.0
    },
    {
        "text": "So if you did array dot, double\nunderscore, proto, double underscore,",
        "start": 3056.69,
        "duration": 5.3
    },
    {
        "text": "we see this large object with\na bunch of different functions.",
        "start": 3061.99,
        "duration": 6.0
    },
    {
        "text": "And so we see down here, push, which\nis that one that we invoked earlier.",
        "start": 3067.99,
        "duration": 7.45
    },
    {
        "text": "So this is exactly how it knows\nwhere that push implementation is.",
        "start": 3075.44,
        "duration": 4.13
    },
    {
        "text": "And so we can do\narr.__proto__.__proto__,",
        "start": 3079.57,
        "duration": 5.68
    },
    {
        "text": "and go even farther up the chain.",
        "start": 3085.25,
        "duration": 2.15
    },
    {
        "text": "So this one has a bunch of other\nones toString value of, whatever.",
        "start": 3087.4,
        "duration": 4.66
    },
    {
        "text": "And if you notice, both the arrays\nprototype, and it's arrays prototypes",
        "start": 3092.06,
        "duration": 6.14
    },
    {
        "text": "prototype, have this\nmethod called toString.",
        "start": 3098.2,
        "duration": 4.32
    },
    {
        "text": "And if I were to invoke\narr.toString which one of these",
        "start": 3102.52,
        "duration": 5.22
    },
    {
        "text": "is going to actually get called?",
        "start": 3107.74,
        "duration": 1.47
    },
    {
        "text": "AUDIENCE: The second one.",
        "start": 3113.575,
        "duration": 1.287
    },
    {
        "text": "JORDAN: The second one?",
        "start": 3114.862,
        "duration": 0.958
    },
    {
        "text": "Which one is the second one?",
        "start": 3115.82,
        "duration": 0.96
    },
    {
        "text": "AUDIENCE: Dot proto, dot proto.",
        "start": 3116.78,
        "duration": 1.291
    },
    {
        "text": "[INAUDIBLE]",
        "start": 3118.071,
        "duration": 0.631
    },
    {
        "text": "JORDAN: Dot proto, dot proto.",
        "start": 3118.702,
        "duration": 1.208
    },
    {
        "text": "So, actually the opposite.",
        "start": 3119.91,
        "duration": 2.17
    },
    {
        "text": "So, since the toString,\non the array prototype,",
        "start": 3122.08,
        "duration": 5.98
    },
    {
        "text": "is more specific than the toSting\nmethod on the object prototype,",
        "start": 3128.06,
        "duration": 4.14
    },
    {
        "text": "this one is going to get invoked.",
        "start": 3132.2,
        "duration": 3.21
    },
    {
        "text": "Because its, just because\nits more specific.",
        "start": 3135.41,
        "duration": 2.49
    },
    {
        "text": "Because an array is an\narray and its an object.",
        "start": 3137.9,
        "duration": 3.666
    },
    {
        "text": "But its more specific to call it an\narray, than to call it an object.",
        "start": 3141.566,
        "duration": 2.874
    },
    {
        "text": "So its going to invoke\nthe one on the array.",
        "start": 3144.44,
        "duration": 2.754
    },
    {
        "text": "Does that makes sense?",
        "start": 3147.194,
        "duration": 0.916
    },
    {
        "text": "Anybody have a question about that?",
        "start": 3150.392,
        "duration": 1.458
    },
    {
        "text": "It's an important concept, and\na little bit confusing at first.",
        "start": 3151.85,
        "duration": 3.46
    },
    {
        "text": "Cool.",
        "start": 3160.4,
        "duration": 0.5
    },
    {
        "text": "Most primitive types\nhad object wrappers.",
        "start": 3160.9,
        "duration": 2.91
    },
    {
        "text": "And so we talked about\nhow primitive types don't",
        "start": 3163.81,
        "duration": 3.24
    },
    {
        "text": "have any methods associated with them.",
        "start": 3167.05,
        "duration": 4.46
    },
    {
        "text": "But primitive types\nalso have wrappers that",
        "start": 3171.51,
        "duration": 2.44
    },
    {
        "text": "have prototypes associated with them.",
        "start": 3173.95,
        "duration": 3.78
    },
    {
        "text": "What the heck does that mean?",
        "start": 3177.73,
        "duration": 1.27
    },
    {
        "text": "So if I were to do\n42.toString, It's going",
        "start": 3179.0,
        "duration": 3.189
    },
    {
        "text": "to be like what the heck do you mean?",
        "start": 3182.189,
        "duration": 1.541
    },
    {
        "text": "42.toString--",
        "start": 3183.73,
        "duration": 0.541
    },
    {
        "text": "[TYPING]",
        "start": 3184.271,
        "duration": 2.309
    },
    {
        "text": "Right I told you that these\nprimitive values don't have methods.",
        "start": 3186.58,
        "duration": 5.85
    },
    {
        "text": "And so 42.toString\ndoesn't really make sense.",
        "start": 3192.43,
        "duration": 3.25
    },
    {
        "text": "But say I were to do this thing\nconst num = 42 and did num.toString,",
        "start": 3195.68,
        "duration": 5.33
    },
    {
        "text": "[TYPING]",
        "start": 3201.01,
        "duration": 1.05
    },
    {
        "text": "That will actually do something.",
        "start": 3202.06,
        "duration": 1.407
    },
    {
        "text": "And that's a little bit strange.",
        "start": 3203.467,
        "duration": 1.333
    },
    {
        "text": "This is another one of those\nJavaScript interesting behaviors.",
        "start": 3204.8,
        "duration": 4.67
    },
    {
        "text": "Because all of the primitive\nvalues have wrappers",
        "start": 3209.47,
        "duration": 3.45
    },
    {
        "text": "that give them access\nto a bunch of methods.",
        "start": 3212.92,
        "duration": 3.69
    },
    {
        "text": "And JavaScript will automatically\ndo what's called boxing for you.",
        "start": 3216.61,
        "duration": 3.98
    },
    {
        "text": "Which it says, hey, like\nI know 42 is a primitive,",
        "start": 3220.59,
        "duration": 3.222
    },
    {
        "text": "but if you call this toString\nmethod, I know what you mean.",
        "start": 3223.812,
        "duration": 2.458
    },
    {
        "text": "I'm going to box this 42\nnumber with this prototype that",
        "start": 3226.27,
        "duration": 3.93
    },
    {
        "text": "has a bunch of these methods on it.",
        "start": 3230.2,
        "duration": 2.272
    },
    {
        "text": "So if I were to do 42.toString\nthat would make sense.",
        "start": 3232.472,
        "duration": 2.208
    },
    {
        "text": "And if I num.__proto__,",
        "start": 3234.68,
        "duration": 2.81
    },
    {
        "text": "[TYPING]",
        "start": 3237.49,
        "duration": 3.13
    },
    {
        "text": "That actually exists.",
        "start": 3240.62,
        "duration": 1.31
    },
    {
        "text": "But 42.__proto__",
        "start": 3241.93,
        "duration": 0.75
    },
    {
        "text": "[TYPING]",
        "start": 3242.68,
        "duration": 3.3
    },
    {
        "text": "Does not.",
        "start": 3245.98,
        "duration": 0.878
    },
    {
        "text": "Does that make sense?",
        "start": 3246.858,
        "duration": 1.464
    },
    {
        "text": "Another way to find out if a\nvalue is an instance of some type,",
        "start": 3256.14,
        "duration": 5.23
    },
    {
        "text": "you can do this thing\ncalled x instance of number.",
        "start": 3261.37,
        "duration": 3.054
    },
    {
        "text": "And that would return false.",
        "start": 3264.424,
        "duration": 1.166
    },
    {
        "text": "Because x is actually not\nof type capital number,",
        "start": 3265.59,
        "duration": 2.87
    },
    {
        "text": "it's just boxed around that\nnumber object for your reference.",
        "start": 3268.46,
        "duration": 6.906
    },
    {
        "text": "Does that make sense?",
        "start": 3275.366,
        "duration": 0.874
    },
    {
        "text": "Again not something you're going to\nuse everyday, just something that",
        "start": 3279.966,
        "duration": 2.874
    },
    {
        "text": "is helpful to know in case you\nrun into the strange corner cases.",
        "start": 3282.84,
        "duration": 2.708
    },
    {
        "text": "Cool.",
        "start": 3289.52,
        "duration": 0.91
    },
    {
        "text": "So why would we use a\nreference to the prototype?",
        "start": 3290.43,
        "duration": 3.21
    },
    {
        "text": "And what is the alternative there?",
        "start": 3293.64,
        "duration": 1.74
    },
    {
        "text": "Anybody care to give a shot at that?",
        "start": 3295.38,
        "duration": 1.5
    },
    {
        "text": "So this is going back a little bit too\ndeep copying versus shallow copying.",
        "start": 3306.6,
        "duration": 3.9
    },
    {
        "text": "AUDIENCE: So, maybe if the\ninitial object is massive.",
        "start": 3310.5,
        "duration": 3.8
    },
    {
        "text": "And then you just want to do\nsomething, like, after it?",
        "start": 3314.3,
        "duration": 4.28
    },
    {
        "text": "JORDAN: Yeah, so if the initial object\nis massive, like, what happens then?",
        "start": 3318.58,
        "duration": 4.13
    },
    {
        "text": "So the alternative is basically\nto clone every single--",
        "start": 3322.71,
        "duration": 3.695
    },
    {
        "text": "to deep copy every single\nprototype every single time",
        "start": 3326.405,
        "duration": 2.665
    },
    {
        "text": "you couldn't new value.",
        "start": 3329.07,
        "duration": 1.29
    },
    {
        "text": "Which is, safe, because that\nnumber and all of its methods",
        "start": 3330.36,
        "duration": 5.07
    },
    {
        "text": "are all encapsulated within\nthat specific variable.",
        "start": 3335.43,
        "duration": 3.69
    },
    {
        "text": "But it's also a little bit\nexpensive in both performance,",
        "start": 3339.12,
        "duration": 2.64
    },
    {
        "text": "because you have to do that\ndeep copy every single time.",
        "start": 3341.76,
        "duration": 2.43
    },
    {
        "text": "And also of memory, because the\nobject starts to get pretty large.",
        "start": 3344.19,
        "duration": 3.16
    },
    {
        "text": "And if you have an array of\nlike 100 different things,",
        "start": 3347.35,
        "duration": 2.93
    },
    {
        "text": "all hundreds of those, deep copying\nevery single prototype gets pretty big.",
        "start": 3350.28,
        "duration": 3.9
    },
    {
        "text": "And so what is the danger of storing\na reference to the prototype,",
        "start": 3356.75,
        "duration": 3.19
    },
    {
        "text": "rather than copying the whole thing?",
        "start": 3359.94,
        "duration": 5.605
    },
    {
        "text": "AUDIENCE: I guess if\nchange it, [INAUDIBLE]..",
        "start": 3365.545,
        "duration": 3.985
    },
    {
        "text": "JORDAN: Yeah exactly.",
        "start": 3369.53,
        "duration": 1.11
    },
    {
        "text": "If you change it, then it changes\nfor every single value of that type.",
        "start": 3370.64,
        "duration": 3.66
    },
    {
        "text": "So let's do that really quick.",
        "start": 3376.83,
        "duration": 1.52
    },
    {
        "text": "So, so say we have, so we solved\nnum, which is equal to 42, right?",
        "start": 3378.35,
        "duration": 7.93
    },
    {
        "text": "And if you do num.toString,\nwhat so we expect to come out?",
        "start": 3386.28,
        "duration": 4.49
    },
    {
        "text": "42 is a string right?",
        "start": 3390.77,
        "duration": 1.67
    },
    {
        "text": "But say, some devious\nprogrammer was doing this thing",
        "start": 3392.44,
        "duration": 2.807
    },
    {
        "text": "where he did number.prototype.toString",
        "start": 3395.247,
        "duration": 1.583
    },
    {
        "text": "[TYPING]",
        "start": 3396.83,
        "duration": 2.644
    },
    {
        "text": "And you actually override that to be\nsome function that will return 100.",
        "start": 3402.7,
        "duration": 10.0
    },
    {
        "text": "Now what happens if I\ncall a num.toString?",
        "start": 3412.7,
        "duration": 3.36
    },
    {
        "text": "Wait a second.",
        "start": 3416.06,
        "duration": 1.03
    },
    {
        "text": "[TYPING]",
        "start": 3417.09,
        "duration": 1.907
    },
    {
        "text": "So that could have some\ndangerous penalties right?",
        "start": 3418.997,
        "duration": 2.083
    },
    {
        "text": "So if I were to change the\nprototype of the number class,",
        "start": 3421.08,
        "duration": 3.67
    },
    {
        "text": "even though num was declared 100\nlines prior to be the number 42.",
        "start": 3424.75,
        "duration": 6.2
    },
    {
        "text": "And we tried num.toString\nhere and it returned 42.",
        "start": 3430.95,
        "duration": 3.81
    },
    {
        "text": "If we were to change\nthe prototype later,",
        "start": 3434.76,
        "duration": 2.1
    },
    {
        "text": "it affects everything\nthat has ever happened.",
        "start": 3436.86,
        "duration": 2.97
    },
    {
        "text": "So num.toString now\nstarts returning 100.",
        "start": 3439.83,
        "duration": 2.37
    },
    {
        "text": "And everything that will happen.",
        "start": 3442.2,
        "duration": 1.36
    },
    {
        "text": "So if I were to do--",
        "start": 3443.56,
        "duration": 0.833
    },
    {
        "text": "[TYPING]",
        "start": 3444.393,
        "duration": 3.288
    },
    {
        "text": "Everything in the future\nalso has those consequences.",
        "start": 3452.04,
        "duration": 2.86
    },
    {
        "text": "So changing the prototype is\nsomething that is very dangerous,",
        "start": 3454.9,
        "duration": 2.99
    },
    {
        "text": "and is recommended against doing.",
        "start": 3457.89,
        "duration": 3.032
    },
    {
        "text": "Does that make sense?",
        "start": 3460.922,
        "duration": 1.488
    },
    {
        "text": "Cool.",
        "start": 3466.374,
        "duration": 0.5
    },
    {
        "text": "So let's actually take a short break.",
        "start": 3472.83,
        "duration": 3.1
    },
    {
        "text": "All right welcome back.",
        "start": 3475.93,
        "duration": 1.78
    },
    {
        "text": "So let's talk about scope now.",
        "start": 3477.71,
        "duration": 3.47
    },
    {
        "text": "So what the heck is scope?",
        "start": 3481.18,
        "duration": 1.2
    },
    {
        "text": "So Scope is a term that's\ntalking about variable lifetime,",
        "start": 3482.38,
        "duration": 3.42
    },
    {
        "text": "and how long these\nvariables actually exist.",
        "start": 3485.8,
        "duration": 1.875
    },
    {
        "text": "And so there are a couple\ndifferent types of scoping.",
        "start": 3490.162,
        "duration": 2.208
    },
    {
        "text": "There's lexical scoping, which is\nthat keyword var that you might",
        "start": 3492.37,
        "duration": 2.85
    },
    {
        "text": "see if you're reading old JavaScript.",
        "start": 3495.22,
        "duration": 2.84
    },
    {
        "text": "And there's block scoping, which\nrefers to how things like const or let",
        "start": 3498.06,
        "duration": 5.23
    },
    {
        "text": "are scoped.",
        "start": 3503.29,
        "duration": 1.05
    },
    {
        "text": "So lexical scoping is basically\nsaying, hey, give me a variable",
        "start": 3504.34,
        "duration": 4.27
    },
    {
        "text": "and it will exist for\nas long as since it",
        "start": 3508.61,
        "duration": 2.27
    },
    {
        "text": "was declared all the way until the\nend of a function ends or the file",
        "start": 3510.88,
        "duration": 4.8
    },
    {
        "text": "if it's in a file.",
        "start": 3515.68,
        "duration": 1.5
    },
    {
        "text": "Whereas the analog\nwould be block scoping",
        "start": 3517.18,
        "duration": 1.92
    },
    {
        "text": "where it behaves a lot like\nsomething behaves in C.",
        "start": 3519.1,
        "duration": 3.62
    },
    {
        "text": "Where basically a\nvariable will be around",
        "start": 3522.72,
        "duration": 3.19
    },
    {
        "text": "from when it's declared until the\nnext end curly brace is reached.",
        "start": 3525.91,
        "duration": 4.6
    },
    {
        "text": "And so that there is the big difference\nbetween var and const and let.",
        "start": 3530.51,
        "duration": 3.65
    },
    {
        "text": "And the difference\nbetween const and let is",
        "start": 3534.16,
        "duration": 2.01
    },
    {
        "text": "that const is something\nthat can't be updated,",
        "start": 3536.17,
        "duration": 2.7
    },
    {
        "text": "meaning if I set a variable\nto be a constant, it",
        "start": 3538.87,
        "duration": 2.82
    },
    {
        "text": "means I'm not going to\nupdate that reference later,",
        "start": 3541.69,
        "duration": 3.51
    },
    {
        "text": "whereas let can be updated.",
        "start": 3545.2,
        "duration": 2.01
    },
    {
        "text": "So if I were to do const thisIsAConst\nand set about equal to something",
        "start": 3547.21,
        "duration": 6.81
    },
    {
        "text": "like 50, if I were to say thisIsAConst\nand try to update that to be 51,",
        "start": 3554.02,
        "duration": 8.79
    },
    {
        "text": "I'm going to get an error actually\nthat says, hey, you call that a const?",
        "start": 3562.81,
        "duration": 4.49
    },
    {
        "text": "But you're trying to change it.",
        "start": 3567.3,
        "duration": 1.49
    },
    {
        "text": "That's not OK.",
        "start": 3568.79,
        "duration": 1.83
    },
    {
        "text": "And so no matter how\nI want to change it--",
        "start": 3570.62,
        "duration": 1.75
    },
    {
        "text": "say I do that plus-plus or\nsomething, that's also going to fail.",
        "start": 3572.37,
        "duration": 3.74
    },
    {
        "text": "Whereas if I did something like\nlet thisIsALet equal to 50,",
        "start": 3576.11,
        "duration": 7.26
    },
    {
        "text": "I can go ahead-- or 51, I made\na typo, but I can just say,",
        "start": 3583.37,
        "duration": 4.32
    },
    {
        "text": "hey, it was a typo, thisIsALet, let me\nchange that to 50 and we're all good.",
        "start": 3587.69,
        "duration": 7.36
    },
    {
        "text": "I mean, I can also do that plus-plus\nor change it however I want",
        "start": 3595.05,
        "duration": 3.12
    },
    {
        "text": "and it will actually update that.",
        "start": 3598.17,
        "duration": 6.16
    },
    {
        "text": "Note that I said the\nreference can't be updated.",
        "start": 3604.33,
        "duration": 4.434
    },
    {
        "text": "I did not say anything about\nthings being immutable.",
        "start": 3608.764,
        "duration": 2.166
    },
    {
        "text": "So if I get const obj equals\nthis empty object, if I then--",
        "start": 3610.93,
        "duration": 9.71
    },
    {
        "text": "I can't update it to be--",
        "start": 3620.64,
        "duration": 2.19
    },
    {
        "text": "point to a different object.",
        "start": 3622.83,
        "duration": 1.23
    },
    {
        "text": "If I try to do obj is something\nelse, I'm going to say,",
        "start": 3624.06,
        "duration": 4.32
    },
    {
        "text": "hey, you call this a const and\nyou're trying to change it.",
        "start": 3628.38,
        "duration": 3.78
    },
    {
        "text": "But I can still do obj.a and set\nthat equal to a, because why?",
        "start": 3632.16,
        "duration": 6.39
    },
    {
        "text": "Anybody care to tell me why?",
        "start": 3638.55,
        "duration": 1.65
    },
    {
        "text": "Exactly.",
        "start": 3646.95,
        "duration": 0.57
    },
    {
        "text": "So the pointer is still\npointing to the same object.",
        "start": 3647.52,
        "duration": 2.43
    },
    {
        "text": "The reference has not changed.",
        "start": 3649.95,
        "duration": 2.83
    },
    {
        "text": "So we mutated that\nobject, but it's still",
        "start": 3652.78,
        "duration": 2.577
    },
    {
        "text": "pointing to that same place in memory.",
        "start": 3655.357,
        "duration": 1.583
    },
    {
        "text": "It's still pointing to the\nobject that exists over here",
        "start": 3656.94,
        "duration": 3.26
    },
    {
        "text": "and that reference has not been changed.",
        "start": 3660.2,
        "duration": 2.44
    },
    {
        "text": "Does that distinction\nmake sense to people?",
        "start": 3662.64,
        "duration": 2.374
    },
    {
        "text": "It's a pretty important one.",
        "start": 3665.014,
        "duration": 1.166
    },
    {
        "text": "Cool So let's play a little bit\nwith these variable lifetimes.",
        "start": 3669.13,
        "duration": 4.953
    },
    {
        "text": "So I said before that if I tried to do\nsomething like this, what happens here?",
        "start": 3689.88,
        "duration": 12.04
    },
    {
        "text": "Error.",
        "start": 3706.275,
        "duration": 0.5
    },
    {
        "text": "Why?",
        "start": 3709.54,
        "duration": 0.5
    },
    {
        "text": "Because it's a constant and\nwe can't update a constant.",
        "start": 3710.04,
        "duration": 3.2
    },
    {
        "text": "And we can confirm this.",
        "start": 3713.24,
        "duration": 2.718
    },
    {
        "text": "Oh.",
        "start": 3715.958,
        "duration": 1.104
    },
    {
        "text": "It'll actually tell\nus, hey, a TypeError.",
        "start": 3717.062,
        "duration": 1.708
    },
    {
        "text": "You call this a constant variable\nbut you're trying assign it.",
        "start": 3718.77,
        "duration": 2.37
    },
    {
        "text": "That's not OK.",
        "start": 3721.14,
        "duration": 0.583
    },
    {
        "text": "But if we did--",
        "start": 3728.51,
        "duration": 0.82
    },
    {
        "text": "this is OK because the reference\nto that object did not change,",
        "start": 3741.05,
        "duration": 3.58
    },
    {
        "text": "it's just mutated it.",
        "start": 3744.63,
        "duration": 1.82
    },
    {
        "text": "On the other side, if we did something\nlike let thisIsALet A Let equal to 51,",
        "start": 3746.45,
        "duration": 7.92
    },
    {
        "text": "and then want to change that\nlater, we go 50, that's totally OK.",
        "start": 3754.37,
        "duration": 6.04
    },
    {
        "text": "But if I actually tried to\nreassign-- so let thisIsALet.",
        "start": 3763.3,
        "duration": 5.87
    },
    {
        "text": "If I tried to do this again, it's going\nto yell at me because it's saying, hey,",
        "start": 3769.17,
        "duration": 3.78
    },
    {
        "text": "you already declared\nsomething called thisIsALet.",
        "start": 3772.95,
        "duration": 2.22
    },
    {
        "text": "You cannot declare that again.",
        "start": 3775.17,
        "duration": 2.64
    },
    {
        "text": "And so const and let\nactually protect you",
        "start": 3777.81,
        "duration": 1.71
    },
    {
        "text": "from declaring something with the same\nvariable name twice, which is something",
        "start": 3779.52,
        "duration": 4.8
    },
    {
        "text": "that var does not do.",
        "start": 3784.32,
        "duration": 0.97
    },
    {
        "text": "Cool.",
        "start": 3804.37,
        "duration": 0.69
    },
    {
        "text": "What do you guys think would\nhappen if I tried to do this?",
        "start": 3805.06,
        "duration": 2.416
    },
    {
        "text": "Anybody care to guess?",
        "start": 3817.83,
        "duration": 1.03
    },
    {
        "text": "Undefined?",
        "start": 3821.85,
        "duration": 1.66
    },
    {
        "text": "So let's try to run it.",
        "start": 3823.51,
        "duration": 2.8
    },
    {
        "text": "Error.",
        "start": 3826.31,
        "duration": 1.03
    },
    {
        "text": "So since these things\nare block scoped, it",
        "start": 3827.34,
        "duration": 2.55
    },
    {
        "text": "means the variable is declared\nat the line that it is written.",
        "start": 3829.89,
        "duration": 4.59
    },
    {
        "text": "And if we try to use it before then,\nit actually does not even exist at all.",
        "start": 3834.48,
        "duration": 3.64
    },
    {
        "text": "So if I tried to console.log something\ncalled thisIsAConst here, remember,",
        "start": 3838.12,
        "duration": 3.14
    },
    {
        "text": "the JavaScript interpreter\nis just reading down",
        "start": 3841.26,
        "duration": 3.24
    },
    {
        "text": "and it won't see like, hey,\nwhat the heck is thisIsAConst?",
        "start": 3844.5,
        "duration": 2.42
    },
    {
        "text": "I have no idea what that is so\nI'm just going to Error here.",
        "start": 3846.92,
        "duration": 2.5
    },
    {
        "text": "Same thing if I tried to\ndo this as a let here.",
        "start": 3852.66,
        "duration": 3.6
    },
    {
        "text": "That will also Error\nwith the same error.",
        "start": 3856.26,
        "duration": 2.246
    },
    {
        "text": "AUDIENCE: So what's line 14 error on?",
        "start": 3858.506,
        "duration": 4.444
    },
    {
        "text": "JORDAN: Why does it error?",
        "start": 3862.95,
        "duration": 2.16
    },
    {
        "text": "Because we're trying to declare two\nvariables with the same variable",
        "start": 3865.11,
        "duration": 4.59
    },
    {
        "text": "name twice.",
        "start": 3869.7,
        "duration": 1.02
    },
    {
        "text": "So we have let thisIsALet equal\n51 here, and we try to do it again",
        "start": 3870.72,
        "duration": 3.6
    },
    {
        "text": "and it's saying, hey, you already\nhave a variable called thisIsALet,",
        "start": 3874.32,
        "duration": 3.06
    },
    {
        "text": "so I'm not going to allow\nyou to do that again.",
        "start": 3877.38,
        "duration": 2.5
    },
    {
        "text": "So it's going to be\nthis error right here.",
        "start": 3879.88,
        "duration": 3.398
    },
    {
        "text": "AUDIENCE: So it's the\ninstantiation of it?",
        "start": 3883.278,
        "duration": 2.891
    },
    {
        "text": "JORDAN: Yeah.",
        "start": 3886.169,
        "duration": 0.541
    },
    {
        "text": "It's saying like-- basically I'm\nsaying, hey, give me a variable to call,",
        "start": 3886.71,
        "duration": 3.219
    },
    {
        "text": "this is a let here, and then a\ncouple lines later I'm saying,",
        "start": 3889.929,
        "duration": 2.541
    },
    {
        "text": "hey, give me a variable\ncalled thisIsALet,",
        "start": 3892.47,
        "duration": 1.77
    },
    {
        "text": "and JavaScript says,\nhey, like, you already",
        "start": 3894.24,
        "duration": 2.19
    },
    {
        "text": "have a block scope\nvariable called thisIsALet,",
        "start": 3896.43,
        "duration": 4.23
    },
    {
        "text": "so I can't give you another one.",
        "start": 3900.66,
        "duration": 3.359
    },
    {
        "text": "However, if I tried to just update\nit like this, that's totally OK.",
        "start": 3904.019,
        "duration": 2.791
    },
    {
        "text": "Any other questions here?",
        "start": 3909.489,
        "duration": 1.041
    },
    {
        "text": "So the other thing we said, we can\nhave these things called a var.",
        "start": 3913.79,
        "duration": 3.27
    },
    {
        "text": "If I did var thisIsAVar equal to\n50, that's fine, I can update it.",
        "start": 3917.06,
        "duration": 8.01
    },
    {
        "text": "That's also fine.",
        "start": 3929.21,
        "duration": 0.87
    },
    {
        "text": "I can also do this, and\nthat won't yell at me.",
        "start": 3930.08,
        "duration": 8.35
    },
    {
        "text": "So vars are older ways\nto declare variables",
        "start": 3938.43,
        "duration": 4.437
    },
    {
        "text": "and they don't have the same\nprotection that let and const do.",
        "start": 3942.867,
        "duration": 2.583
    },
    {
        "text": "You can override them like\nthis and it's totally OK.",
        "start": 3945.45,
        "duration": 4.532
    },
    {
        "text": "And you can actually declare a whole\nnew variable with the same variable name",
        "start": 3949.982,
        "duration": 3.208
    },
    {
        "text": "and that's also OK.",
        "start": 3953.19,
        "duration": 2.67
    },
    {
        "text": "And something-- yeah?",
        "start": 3955.86,
        "duration": 0.991
    },
    {
        "text": "It just-- yeah, so that's--",
        "start": 3960.08,
        "duration": 3.11
    },
    {
        "text": "So if I try to run this,\nit will update the old one.",
        "start": 3983.27,
        "duration": 4.02
    },
    {
        "text": "It'll just replace that value.",
        "start": 3987.29,
        "duration": 1.25
    },
    {
        "text": "It's actually called shadowing,\nwhere you create a new variable",
        "start": 3988.54,
        "duration": 2.71
    },
    {
        "text": "with the same variable name\nwhich basically just overshadows",
        "start": 3991.25,
        "duration": 2.88
    },
    {
        "text": "that old one.",
        "start": 3994.13,
        "duration": 0.66
    },
    {
        "text": "So it's as if the\nother one didn't exist.",
        "start": 3994.79,
        "duration": 1.77
    },
    {
        "text": "Cool, so check this out.",
        "start": 4002.63,
        "duration": 1.17
    },
    {
        "text": "So this errors and we know this errors.",
        "start": 4008.22,
        "duration": 2.87
    },
    {
        "text": "But say I were to do this.",
        "start": 4011.09,
        "duration": 3.73
    },
    {
        "text": "You'd expect this to also\nerror, but actually it does not.",
        "start": 4014.82,
        "duration": 6.11
    },
    {
        "text": "It returns undefined.",
        "start": 4020.93,
        "duration": 2.361
    },
    {
        "text": "So this is another weird\nthing about JavaScript.",
        "start": 4023.291,
        "duration": 1.999
    },
    {
        "text": "This is called hoisting.",
        "start": 4025.29,
        "duration": 2.129
    },
    {
        "text": "And so certain things\nare hoisted, which it",
        "start": 4027.419,
        "duration": 1.791
    },
    {
        "text": "means basically it takes\nthe definition of something",
        "start": 4029.21,
        "duration": 3.63
    },
    {
        "text": "and hoists it to the very top\nof the file and does that first.",
        "start": 4032.84,
        "duration": 3.06
    },
    {
        "text": "Get",
        "start": 4039.07,
        "duration": 0.742
    },
    {
        "text": "And a few things are hoisted.",
        "start": 4039.812,
        "duration": 1.648
    },
    {
        "text": "Var the-- actually, the declaration\nof the creation of an empty variable",
        "start": 4041.46,
        "duration": 5.04
    },
    {
        "text": "are hoisted.",
        "start": 4046.5,
        "duration": 1.38
    },
    {
        "text": "Function definitions are hoisted\nas well, but const and let",
        "start": 4047.88,
        "duration": 3.28
    },
    {
        "text": "are not, as we saw if we tried to access\nthe variable name of the const or let,",
        "start": 4051.16,
        "duration": 4.01
    },
    {
        "text": "then it errors.",
        "start": 4055.17,
        "duration": 0.86
    },
    {
        "text": "But with a var, the declaration of\nthat variable is actually hoisted.",
        "start": 4056.03,
        "duration": 5.289
    },
    {
        "text": "And we can talk a little bit more\nabout how that works in a second,",
        "start": 4061.319,
        "duration": 2.791
    },
    {
        "text": "but let's actually play\nwith it a little bit more.",
        "start": 4064.11,
        "duration": 2.23
    },
    {
        "text": "So function definitions are hoisted.",
        "start": 4066.34,
        "duration": 2.33
    },
    {
        "text": "So let's clean up this\nfile a little bit.",
        "start": 4068.67,
        "duration": 3.92
    },
    {
        "text": "So let's call this\nnew function, called--",
        "start": 4079.332,
        "duration": 1.708
    },
    {
        "text": "so this is console.log.",
        "start": 4087.262,
        "duration": 1.768
    },
    {
        "text": "So I defined this function\ncalled thisIsHoisted",
        "start": 4104.302,
        "duration": 1.958
    },
    {
        "text": "at the very bottom of the file.",
        "start": 4106.26,
        "duration": 1.5
    },
    {
        "text": "And all it does is it\nconsole.logs, there's",
        "start": 4107.76,
        "duration": 2.4
    },
    {
        "text": "a function declared at\nthe bottom of the file.",
        "start": 4110.16,
        "duration": 2.01
    },
    {
        "text": "But something very interesting is at the\nvery top of this file, I can call it.",
        "start": 4112.17,
        "duration": 3.689
    },
    {
        "text": "And that will actually work.",
        "start": 4120.884,
        "duration": 1.166
    },
    {
        "text": "And so that is what's\ncalled function hoisting.",
        "start": 4125.229,
        "duration": 4.88
    },
    {
        "text": "The behavior whereby\na function definition",
        "start": 4130.109,
        "duration": 3.221
    },
    {
        "text": "declared at the very bottom of a\nfile is actually available for use",
        "start": 4133.33,
        "duration": 3.84
    },
    {
        "text": "at the very top of the file as well.",
        "start": 4137.17,
        "duration": 1.5
    },
    {
        "text": "But this does not work in other cases.",
        "start": 4141.34,
        "duration": 2.523
    },
    {
        "text": "So say I were to do something like this.",
        "start": 4143.863,
        "duration": 1.666
    },
    {
        "text": "So who can tell me what the difference\nis between line 21 and line 25?",
        "start": 4166.26,
        "duration": 4.485
    },
    {
        "text": "They look pretty similar, right?",
        "start": 4173.42,
        "duration": 1.559
    },
    {
        "text": "Yeah?",
        "start": 4174.979,
        "duration": 0.499
    },
    {
        "text": "OK.",
        "start": 4180.62,
        "duration": 0.5
    },
    {
        "text": "Yep.",
        "start": 4189.279,
        "duration": 0.5
    },
    {
        "text": "So repeating for the camera, line 25,\nthisIsHoisted is declared as a constant",
        "start": 4189.779,
        "duration": 4.921
    },
    {
        "text": "so it cannot be changed, whereas line 21\nis declared as a function and so it can",
        "start": 4194.7,
        "duration": 5.13
    },
    {
        "text": "be changed, which is absolutely correct.",
        "start": 4199.83,
        "duration": 2.59
    },
    {
        "text": "What happens if I try\nto do this up here?",
        "start": 4202.42,
        "duration": 1.98
    },
    {
        "text": "Yeah, so we're going to get an error.",
        "start": 4212.74,
        "duration": 4.38
    },
    {
        "text": "thisIsHoisted is not defined, but why?",
        "start": 4217.12,
        "duration": 4.2
    },
    {
        "text": "Because as we talked about\nearlier, these things",
        "start": 4221.32,
        "duration": 2.19
    },
    {
        "text": "called consts are not available for\nuse until they're actually declared.",
        "start": 4223.51,
        "duration": 4.74
    },
    {
        "text": "So certain things are hoisted.",
        "start": 4228.25,
        "duration": 2.11
    },
    {
        "text": "Var.",
        "start": 4230.36,
        "duration": 0.65
    },
    {
        "text": "So the declaration of these\nvariables are hoisted.",
        "start": 4231.01,
        "duration": 2.7
    },
    {
        "text": "Function definitions if they're\ndeclared like this are hoisted.",
        "start": 4233.71,
        "duration": 3.39
    },
    {
        "text": "But if we create what's\ncalled an anonymous function,",
        "start": 4237.1,
        "duration": 2.28
    },
    {
        "text": "a function without any name,\nand set that equal to--",
        "start": 4239.38,
        "duration": 4.89
    },
    {
        "text": "or assign that to be a constant,\nthen that constant is not created.",
        "start": 4244.27,
        "duration": 7.08
    },
    {
        "text": "Does that make sense?",
        "start": 4251.35,
        "duration": 3.25
    },
    {
        "text": "So what happens if I try to do this?",
        "start": 4254.6,
        "duration": 3.69
    },
    {
        "text": "Yeah, so same thing.",
        "start": 4258.29,
        "duration": 1.985
    },
    {
        "text": "It errors.",
        "start": 4260.275,
        "duration": 3.06
    },
    {
        "text": "What happens if I try to do this?",
        "start": 4263.335,
        "duration": 1.375
    },
    {
        "text": "What's hoisted?",
        "start": 4268.165,
        "duration": 0.625
    },
    {
        "text": "So notice-- so notice the\ndifference in the two errors.",
        "start": 4279.038,
        "duration": 12.062
    },
    {
        "text": "They're actually not\nthe exact same error.",
        "start": 4291.1,
        "duration": 3.07
    },
    {
        "text": "So who wants to give a guess\nat what's going on here?",
        "start": 4294.17,
        "duration": 4.45
    },
    {
        "text": "So when I declared it with a let\nthat's saying reference error,",
        "start": 4298.62,
        "duration": 3.53
    },
    {
        "text": "thisIsHoisted is not defined,\nwhereas when I use a var,",
        "start": 4302.15,
        "duration": 3.22
    },
    {
        "text": "it says TypeError,\nthisIsHoisted is not a function.",
        "start": 4305.37,
        "duration": 3.871
    },
    {
        "text": "Why might that be?",
        "start": 4309.241,
        "duration": 0.749
    },
    {
        "text": "Yeah?",
        "start": 4309.99,
        "duration": 0.5
    },
    {
        "text": "Uh huh.",
        "start": 4317.07,
        "duration": 0.99
    },
    {
        "text": "Exactly.",
        "start": 4324.02,
        "duration": 1.266
    },
    {
        "text": "So repeating for the camera., and\nI'll bring up the code as well.",
        "start": 4325.286,
        "duration": 2.708
    },
    {
        "text": "So down here, so the first time\nwhen we declared this with the let,",
        "start": 4333.91,
        "duration": 4.77
    },
    {
        "text": "it's not declared at all.",
        "start": 4338.68,
        "duration": 2.47
    },
    {
        "text": "This variable does not exist at all.",
        "start": 4341.15,
        "duration": 1.98
    },
    {
        "text": "So this is not hoisted,\nthe JavaScript does not",
        "start": 4343.13,
        "duration": 2.81
    },
    {
        "text": "know what that means on line 1.",
        "start": 4345.94,
        "duration": 2.53
    },
    {
        "text": "But when I use a var\nhere, remember, it hoists",
        "start": 4348.47,
        "duration": 3.26
    },
    {
        "text": "the declaration of this variable.",
        "start": 4351.73,
        "duration": 1.44
    },
    {
        "text": "So it creates a variable\ncalled thisIsHoisted.",
        "start": 4353.17,
        "duration": 2.58
    },
    {
        "text": "However, it does not assign it a\nvalue until line 25 is executed.",
        "start": 4355.75,
        "duration": 4.05
    },
    {
        "text": "And so at line 1, thisIsHoisted exists.",
        "start": 4359.8,
        "duration": 3.33
    },
    {
        "text": "It's just equal to undefined.",
        "start": 4363.13,
        "duration": 1.87
    },
    {
        "text": "And if I try to invoke\nit like a function,",
        "start": 4365.0,
        "duration": 2.2
    },
    {
        "text": "it says, hey, this is\nan undefined variable,",
        "start": 4367.2,
        "duration": 2.62
    },
    {
        "text": "I can't invoke it like a\nfunction, this is a TypeError.",
        "start": 4369.82,
        "duration": 3.21
    },
    {
        "text": "And so even though both of these things\nerrored, the reason that they errored",
        "start": 4373.03,
        "duration": 4.11
    },
    {
        "text": "is slightly different.",
        "start": 4377.14,
        "duration": 1.11
    },
    {
        "text": "In case one when they're\ndeclared using a const or a let,",
        "start": 4378.25,
        "duration": 4.04
    },
    {
        "text": "that variable just\ndoes not exist at all.",
        "start": 4382.29,
        "duration": 2.45
    },
    {
        "text": "However, when we declared\nusing var, the variable exists.",
        "start": 4384.74,
        "duration": 3.83
    },
    {
        "text": "It's just undefined, and so if we\ntry to invoke it like a function,",
        "start": 4388.57,
        "duration": 3.18
    },
    {
        "text": "and it says, hey, like, this is\nundefined, it's not a function.",
        "start": 4391.75,
        "duration": 4.08
    },
    {
        "text": "Does that make sense to everyone?",
        "start": 4395.83,
        "duration": 2.079
    },
    {
        "text": "So why does this happen?",
        "start": 4401.29,
        "duration": 2.84
    },
    {
        "text": "How does this happen?",
        "start": 4404.13,
        "duration": 2.03
    },
    {
        "text": "And the reason is actually\nhow JavaScript is executed.",
        "start": 4406.16,
        "duration": 3.71
    },
    {
        "text": "So there's two phases in the\nexecution of a JavaScript file.",
        "start": 4409.87,
        "duration": 4.89
    },
    {
        "text": "So before executing any code, it\nhas all of the text in front of it,",
        "start": 4414.76,
        "duration": 4.47
    },
    {
        "text": "but it hasn't executed anything,\nit just reads the entire file.",
        "start": 4419.23,
        "duration": 3.837
    },
    {
        "text": "And what's it looking for?",
        "start": 4423.067,
        "duration": 1.083
    },
    {
        "text": "Well one, it's looking for\nanything wrong with the file.",
        "start": 4424.15,
        "duration": 2.91
    },
    {
        "text": "So say like my very first example\nwhen I had an array and it was missing",
        "start": 4427.06,
        "duration": 5.22
    },
    {
        "text": "a comma, that's something that's\ncaught in the first reading.",
        "start": 4432.28,
        "duration": 2.73
    },
    {
        "text": "It says, hey, like, this looks like\nan array but it's not quite right.",
        "start": 4435.01,
        "duration": 3.66
    },
    {
        "text": "Like, I see this thing that I'm not\nexpecting, I'm respecting a comma here.",
        "start": 4438.67,
        "duration": 3.894
    },
    {
        "text": "So that's one thing that's caught.",
        "start": 4442.564,
        "duration": 1.416
    },
    {
        "text": "Other things, maybe it will\nadd some semi-colons for you",
        "start": 4443.98,
        "duration": 3.51
    },
    {
        "text": "and stuff like that.",
        "start": 4447.49,
        "duration": 2.67
    },
    {
        "text": "And then any function definitions\njust get saved in memory.",
        "start": 4450.16,
        "duration": 4.014
    },
    {
        "text": "It says, hey, this is a function,\nlet's put this in memory",
        "start": 4454.174,
        "duration": 2.416
    },
    {
        "text": "so if somebody wants to use\nit at line 1 they're able to.",
        "start": 4456.59,
        "duration": 4.1
    },
    {
        "text": "Variable initializations, if\nthey're lexically scope-- or I mean,",
        "start": 4460.69,
        "duration": 4.35
    },
    {
        "text": "if they're lexically-scoped\nthey will be declared,",
        "start": 4465.04,
        "duration": 2.52
    },
    {
        "text": "but they will not be initialized.",
        "start": 4467.56,
        "duration": 1.56
    },
    {
        "text": "Meaning anything\ndeclared with var will be",
        "start": 4469.12,
        "duration": 2.76
    },
    {
        "text": "declared-- like there's\na variable that exists,",
        "start": 4471.88,
        "duration": 2.28
    },
    {
        "text": "but it's not going to be set\nequal to anything until later.",
        "start": 4474.16,
        "duration": 4.71
    },
    {
        "text": "And then there's a second phase called\nthe execution phase, whereby the code",
        "start": 4478.87,
        "duration": 3.57
    },
    {
        "text": "is actually run, it's executed.",
        "start": 4482.44,
        "duration": 1.89
    },
    {
        "text": "And so that is when things\nlike const or let get invoked--",
        "start": 4484.33,
        "duration": 4.95
    },
    {
        "text": "or get both declared and initialized.",
        "start": 4489.28,
        "duration": 4.14
    },
    {
        "text": "Does that make sense to everyone?",
        "start": 4493.42,
        "duration": 2.124
    },
    {
        "text": "Anybody have any questions on scope?",
        "start": 4498.82,
        "duration": 2.216
    },
    {
        "text": "So why might we take\nadvantage of this scoping?",
        "start": 4505.9,
        "duration": 3.443
    },
    {
        "text": "Does it seem like a feature\nor does it seem like a bug?",
        "start": 4509.343,
        "duration": 2.291
    },
    {
        "text": "Anybody care to guess?",
        "start": 4516.96,
        "duration": 1.314
    },
    {
        "text": "There's no correct answer to this.",
        "start": 4518.274,
        "duration": 1.416
    },
    {
        "text": "It's completely opinion.",
        "start": 4519.69,
        "duration": 1.38
    },
    {
        "text": "Yeah?",
        "start": 4521.07,
        "duration": 0.5
    },
    {
        "text": "AUDIENCE: So you've got a controller\nwith math functions in it.",
        "start": 4521.57,
        "duration": 2.886
    },
    {
        "text": "JORDAN: Uh huh.",
        "start": 4524.456,
        "duration": 0.962
    },
    {
        "text": "AUDIENCE: You can call the\nones there and lay down",
        "start": 4525.418,
        "duration": 2.084
    },
    {
        "text": "a file so that you can write all\nyour code in one giant function?",
        "start": 4527.502,
        "duration": 4.188
    },
    {
        "text": "JORDAN: Yes So, one\nthing might be we can",
        "start": 4531.69,
        "duration": 2.52
    },
    {
        "text": "have these function\ndeclarations at the very bottom",
        "start": 4534.21,
        "duration": 2.454
    },
    {
        "text": "and then we can use it at the top.",
        "start": 4536.664,
        "duration": 1.416
    },
    {
        "text": "And so that might be good\nfor code organization.",
        "start": 4538.08,
        "duration": 2.88
    },
    {
        "text": "Like somebody reading\nyour code would know, hey,",
        "start": 4540.96,
        "duration": 2.16
    },
    {
        "text": "if I'm looking for\nthese functions, they're",
        "start": 4543.12,
        "duration": 2.01
    },
    {
        "text": "all going to be declared\ntogether at the bottom.",
        "start": 4545.13,
        "duration": 2.22
    },
    {
        "text": "And they might be used everywhere,\nbut all the function declarations",
        "start": 4547.35,
        "duration": 3.06
    },
    {
        "text": "are all going to be here.",
        "start": 4550.41,
        "duration": 1.041
    },
    {
        "text": "So that might be a feature because\nit's good for organization.",
        "start": 4551.451,
        "duration": 4.209
    },
    {
        "text": "So say we're to play devil's advocate.",
        "start": 4555.66,
        "duration": 2.91
    },
    {
        "text": "Who might see this as a bug?",
        "start": 4558.57,
        "duration": 2.346
    },
    {
        "text": "Uh huh.",
        "start": 4574.038,
        "duration": 3.162
    },
    {
        "text": "OK.",
        "start": 4577.2,
        "duration": 0.5
    },
    {
        "text": "So the question is, like, why\ncan we declare two variables",
        "start": 4577.7,
        "duration": 2.872
    },
    {
        "text": "with the same name when they look\nlike they're in the same scope,",
        "start": 4580.572,
        "duration": 2.708
    },
    {
        "text": "specifically with this var keyword?",
        "start": 4583.28,
        "duration": 2.82
    },
    {
        "text": "Which is another thing where it's a\nbug/feature that a lot of people use.",
        "start": 4586.1,
        "duration": 5.66
    },
    {
        "text": "And so if JavaScript were to be updated\nand that bug/feature were to disappear,",
        "start": 4591.76,
        "duration": 4.99
    },
    {
        "text": "a lot of code would break.",
        "start": 4596.75,
        "duration": 2.52
    },
    {
        "text": "So a lot of people have\ntook advantage of this.",
        "start": 4599.27,
        "duration": 1.98
    },
    {
        "text": "And basically it's the same thing as\nlike, why is typeof a null object?",
        "start": 4603.862,
        "duration": 2.958
    },
    {
        "text": "Just because it is.",
        "start": 4609.77,
        "duration": 1.08
    },
    {
        "text": "And we can't change that because\npeople rely on that behavior.",
        "start": 4610.85,
        "duration": 4.39
    },
    {
        "text": "I know it's kind of an anti-answer,\nbut does that kind of makes sense?",
        "start": 4615.24,
        "duration": 3.86
    },
    {
        "text": "Yeah, you should-- so there's not\nreally a good reason to use var anymore.",
        "start": 4622.34,
        "duration": 4.99
    },
    {
        "text": "With ES6, everything\nsupports const and let.",
        "start": 4627.33,
        "duration": 3.97
    },
    {
        "text": "And so I've been using them in all\nof the examples except for these.",
        "start": 4631.3,
        "duration": 5.065
    },
    {
        "text": "And I think you should\ndefinitely use them as well.",
        "start": 4636.365,
        "duration": 2.125
    },
    {
        "text": "The reason I'm getting var\nis one, so if you see this,",
        "start": 4638.49,
        "duration": 3.68
    },
    {
        "text": "you know what's kind of going on, and\nbecause a lot of legacy code-- a lot",
        "start": 4642.17,
        "duration": 3.54
    },
    {
        "text": "of code written two, five\nyears ago, 10 years ago",
        "start": 4645.71,
        "duration": 3.18
    },
    {
        "text": "uses var just because\nit was the only option.",
        "start": 4648.89,
        "duration": 1.92
    },
    {
        "text": "One thing that I didn't mention\nearlier is that you can also",
        "start": 4653.76,
        "duration": 3.612
    },
    {
        "text": "declare a variable like this.",
        "start": 4657.372,
        "duration": 1.208
    },
    {
        "text": "So this is another way\nof declaring a variable.",
        "start": 4668.47,
        "duration": 4.08
    },
    {
        "text": "This creates a global variable.",
        "start": 4672.55,
        "duration": 2.517
    },
    {
        "text": "It's something that you probably\nwon't see that often, there's",
        "start": 4675.067,
        "duration": 2.583
    },
    {
        "text": "really no reason to do it.",
        "start": 4677.65,
        "duration": 1.77
    },
    {
        "text": "But in case you ever see\nthat, that's what it is.",
        "start": 4679.42,
        "duration": 4.27
    },
    {
        "text": "So if you declare a variable without\ngiving it a keyword like let, const,",
        "start": 4683.69,
        "duration": 3.555
    },
    {
        "text": "or var, it creates it globally.",
        "start": 4687.245,
        "duration": 2.18
    },
    {
        "text": "But there's no reason for\nyou to use this, really.",
        "start": 4692.23,
        "duration": 3.21
    },
    {
        "text": "It's just if you ever see\nit, that's what it is.",
        "start": 4695.44,
        "duration": 2.398
    },
    {
        "text": "Any questions at all about scoping?",
        "start": 4701.19,
        "duration": 2.38
    },
    {
        "text": "It's a pretty important concept.",
        "start": 4703.57,
        "duration": 3.95
    },
    {
        "text": "And for online folks as well,\nremember, you can post in Slack",
        "start": 4707.52,
        "duration": 3.18
    },
    {
        "text": "and the staff will either field\nthose questions or pass them to me.",
        "start": 4710.7,
        "duration": 4.846
    },
    {
        "text": "Cool So let's move on to\nour final topic of the day.",
        "start": 4719.21,
        "duration": 2.72
    },
    {
        "text": "So the global object.",
        "start": 4726.37,
        "duration": 2.11
    },
    {
        "text": "So the way these things all work\nis basically in any given runtime,",
        "start": 4728.48,
        "duration": 7.46
    },
    {
        "text": "there's this thing\ncalled a global object.",
        "start": 4735.94,
        "duration": 2.65
    },
    {
        "text": "And so all variables, all\nfunctions are actually",
        "start": 4738.59,
        "duration": 2.63
    },
    {
        "text": "keys or parameters or\nmethods on the global object.",
        "start": 4741.22,
        "duration": 3.9
    },
    {
        "text": "So in browser, there's\nthis thing called a window",
        "start": 4745.12,
        "duration": 3.18
    },
    {
        "text": "which is a global object of a window.",
        "start": 4748.3,
        "duration": 1.75
    },
    {
        "text": "So this is a browser environment.",
        "start": 4750.05,
        "duration": 5.78
    },
    {
        "text": "And if I type window, I see this thing.",
        "start": 4755.83,
        "duration": 3.92
    },
    {
        "text": "And it has a lot in it.",
        "start": 4759.75,
        "duration": 4.13
    },
    {
        "text": "But basically the window\nis this global object,",
        "start": 4777.01,
        "duration": 2.27
    },
    {
        "text": "and on it there is all sorts of stuff.",
        "start": 4779.28,
        "duration": 3.01
    },
    {
        "text": "So we see $0, $0a.",
        "start": 4782.29,
        "duration": 3.17
    },
    {
        "text": "So these-- so any variable that\nyou declare in this console",
        "start": 4785.46,
        "duration": 4.47
    },
    {
        "text": "gets put onto this global\nobject called window.",
        "start": 4789.93,
        "duration": 3.96
    },
    {
        "text": "And so actually, let me open\na brand new browser tab.",
        "start": 4793.89,
        "duration": 2.83
    },
    {
        "text": "And we'll get a little\nbit of a cleaner window.",
        "start": 4803.212,
        "duration": 1.958
    },
    {
        "text": "So the reason that we saw these\nthings called $0, $whatever,",
        "start": 4805.17,
        "duration": 3.13
    },
    {
        "text": "is because I open these dev tools on\nthe same tab as my lecture slides.",
        "start": 4808.3,
        "duration": 7.03
    },
    {
        "text": "And the way that Google\nSlides works is since it's",
        "start": 4815.33,
        "duration": 5.79
    },
    {
        "text": "something dynamic on the web,\nit has to be using JavaScript.",
        "start": 4821.12,
        "duration": 3.09
    },
    {
        "text": "And since it's using\nJavaScript, obviously it's",
        "start": 4824.21,
        "duration": 2.01
    },
    {
        "text": "creating a bunch of functions,\nit's creating a bunch of variables.",
        "start": 4826.22,
        "duration": 2.75
    },
    {
        "text": "And all of these things end\nup on the window object.",
        "start": 4828.97,
        "duration": 2.32
    },
    {
        "text": "And so when we check out--\nwhen we inspected the window",
        "start": 4831.29,
        "duration": 2.7
    },
    {
        "text": "object of that particular tab,\nthere was a bunch of stuff",
        "start": 4833.99,
        "duration": 2.79
    },
    {
        "text": "on it because that's how\nGoogle Slides is working.",
        "start": 4836.78,
        "duration": 3.72
    },
    {
        "text": "And when we created a new\ntab, this is a brand new tab",
        "start": 4840.5,
        "duration": 6.66
    },
    {
        "text": "and therefore no JavaScript\nhas been executed,",
        "start": 4847.16,
        "duration": 2.08
    },
    {
        "text": "so there's a lot fewer variables\nand stuff on this new tab.",
        "start": 4849.24,
        "duration": 5.7
    },
    {
        "text": "And so whenever we\ncreate new variables-- so",
        "start": 4854.94,
        "duration": 2.09
    },
    {
        "text": "say we do const x equals this is\na new variable, we see x is this.",
        "start": 4857.03,
        "duration": 7.98
    },
    {
        "text": "We can also do this window.x--",
        "start": 4865.01,
        "duration": 3.76
    },
    {
        "text": "I declare it as a const.",
        "start": 4868.77,
        "duration": 1.5
    },
    {
        "text": "So the way that browser windows\nhandle these blocks of variables",
        "start": 4879.24,
        "duration": 2.71
    },
    {
        "text": "is a little bit different.",
        "start": 4881.95,
        "duration": 1.91
    },
    {
        "text": "So we'll use var for\nthe sake of explanation.",
        "start": 4883.86,
        "duration": 2.92
    },
    {
        "text": "So when I create this new\nvariable called var y,",
        "start": 4886.78,
        "duration": 3.65
    },
    {
        "text": "it is the exact same thing as window.y\nAnd so if we inspect the window,",
        "start": 4890.43,
        "duration": 9.03
    },
    {
        "text": "we see a bunch of things that are part\nof the JavaScript API, the browser",
        "start": 4899.46,
        "duration": 3.38
    },
    {
        "text": "API, all of these things.",
        "start": 4902.84,
        "duration": 2.23
    },
    {
        "text": "And if we go all the\nway to the very bottom,",
        "start": 4905.07,
        "duration": 7.03
    },
    {
        "text": "so this is stuff that is\ncreated in the new tab.",
        "start": 4912.1,
        "duration": 5.258
    },
    {
        "text": "L, M, N, O, P, Q, R,\nS. We see this y here.",
        "start": 4917.358,
        "duration": 5.162
    },
    {
        "text": "So part of that window object\nis that variable called y",
        "start": 4922.52,
        "duration": 3.41
    },
    {
        "text": "that we stuck on the window.",
        "start": 4925.93,
        "duration": 1.55
    },
    {
        "text": "And so even though we declared\nit with var y equals something,",
        "start": 4927.48,
        "duration": 3.31
    },
    {
        "text": "it ended up on that\nglobal object, and that's",
        "start": 4930.79,
        "duration": 2.19
    },
    {
        "text": "how JavaScript keeps track of\nall of your valuables and stuff.",
        "start": 4932.98,
        "duration": 4.98
    },
    {
        "text": "And so what happens when we're in the\nnode environment and we type window?",
        "start": 4937.96,
        "duration": 7.64
    },
    {
        "text": "up window's not defined.",
        "start": 4945.6,
        "duration": 1.692
    },
    {
        "text": "And it's because in\nthe node environment,",
        "start": 4947.292,
        "duration": 1.708
    },
    {
        "text": "the global variable is not called\nwindow, it's actually called global.",
        "start": 4949.0,
        "duration": 3.13
    },
    {
        "text": "And if we type global, we\nnow see all of these things.",
        "start": 4952.13,
        "duration": 5.0
    },
    {
        "text": "And a lot of this will overlap with\nthat window object in the browser,",
        "start": 4959.87,
        "duration": 3.76
    },
    {
        "text": "but since the browser API has\nthings in it that is not necessarily",
        "start": 4963.63,
        "duration": 4.0
    },
    {
        "text": "used in the command line\nstuff like, give me a DOM node",
        "start": 4967.63,
        "duration": 3.6
    },
    {
        "text": "or give me CSS on this DOM node,\nstuff like that, that doesn't really",
        "start": 4971.23,
        "duration": 5.01
    },
    {
        "text": "make sense in a command line\ninterface, therefore those things",
        "start": 4976.24,
        "duration": 5.43
    },
    {
        "text": "are not on this global object.",
        "start": 4981.67,
        "duration": 4.26
    },
    {
        "text": "And then if we try to type\nglobal, here in the window,",
        "start": 4985.93,
        "duration": 6.03
    },
    {
        "text": "that doesn't really make sense either.",
        "start": 4991.96,
        "duration": 3.42
    },
    {
        "text": "There's another thing that's\njust kind of important to know",
        "start": 4995.38,
        "duration": 2.67
    },
    {
        "text": "but you might not ever\ntake advantage of it.",
        "start": 4998.05,
        "duration": 3.589
    },
    {
        "text": "But does that-- does that make sense?",
        "start": 5001.639,
        "duration": 1.541
    },
    {
        "text": "Cool.",
        "start": 5006.18,
        "duration": 0.5
    },
    {
        "text": "So let's move onto something that we'll\ndiscuss a lot more in the next lecture",
        "start": 5009.62,
        "duration": 4.18
    },
    {
        "text": "but I'll go ahead and introduce\nthe concept in this lecture",
        "start": 5013.8,
        "duration": 2.81
    },
    {
        "text": "and leave you with a\nlittle bit of a teaser.",
        "start": 5016.61,
        "duration": 2.52
    },
    {
        "text": "So who here has heard\nof a closure before?",
        "start": 5019.13,
        "duration": 1.86
    },
    {
        "text": "So closures are actually\none of the things",
        "start": 5023.69,
        "duration": 2.94
    },
    {
        "text": "that JavaScript\nprogrammers hate the most",
        "start": 5026.63,
        "duration": 3.252
    },
    {
        "text": "because it's a very, very\ndifficult concept to learn.",
        "start": 5029.882,
        "duration": 2.208
    },
    {
        "text": "Mostly because it's always\ntaught somewhat poorly.",
        "start": 5035.12,
        "duration": 5.07
    },
    {
        "text": "And so next time I'm going to try\nto do a good job of teaching you,",
        "start": 5040.19,
        "duration": 2.8
    },
    {
        "text": "but I'm going to show you right now\nthe problem that a lot of people face.",
        "start": 5042.99,
        "duration": 4.98
    },
    {
        "text": "And so what closures are are functions--",
        "start": 5047.97,
        "duration": 2.74
    },
    {
        "text": "is a behavior whereby functions\nthat refer to variables",
        "start": 5050.71,
        "duration": 2.35
    },
    {
        "text": "declared by a parent\nfunction still exist,",
        "start": 5053.06,
        "duration": 3.22
    },
    {
        "text": "and it's possibly because of scoping.",
        "start": 5056.28,
        "duration": 2.592
    },
    {
        "text": "What the heck does that mean?",
        "start": 5058.872,
        "duration": 1.208
    },
    {
        "text": "I'll explain it in the next\nlecture, but let's go ahead",
        "start": 5060.08,
        "duration": 2.291
    },
    {
        "text": "and explore what this actually means.",
        "start": 5062.371,
        "duration": 4.537
    },
    {
        "text": "All right.",
        "start": 5076.2,
        "duration": 2.48
    },
    {
        "text": "So let's do this.",
        "start": 5078.68,
        "duration": 1.135
    },
    {
        "text": "So first thing I'm\ngoing to do is I'm going",
        "start": 5095.714,
        "duration": 1.791
    },
    {
        "text": "to declare an empty array\ncalled array, and I'm",
        "start": 5097.505,
        "duration": 2.889
    },
    {
        "text": "going to fill that with a few values.",
        "start": 5100.394,
        "duration": 1.541
    },
    {
        "text": "That's And I'm using var intentionally.",
        "start": 5107.6,
        "duration": 5.354
    },
    {
        "text": "And that's push on a\nfunction that does this.",
        "start": 5117.07,
        "duration": 3.22
    },
    {
        "text": "All right So what the\nheck did I do here?",
        "start": 5143.85,
        "duration": 2.38
    },
    {
        "text": "So I declared a function\ncalled makeFunctionArray,",
        "start": 5146.23,
        "duration": 3.54
    },
    {
        "text": "and all it does is it creates an\narray, fill it with functions,",
        "start": 5149.77,
        "duration": 3.33
    },
    {
        "text": "and then invoke one of them.",
        "start": 5153.1,
        "duration": 2.05
    },
    {
        "text": "And so if I were to call this--",
        "start": 5155.15,
        "duration": 1.291
    },
    {
        "text": "if I were to call this, I'd get back\nan array full of functions, right?",
        "start": 5170.68,
        "duration": 4.84
    },
    {
        "text": "And what do we expect those\nfunctions to do? each of them?",
        "start": 5175.52,
        "duration": 3.054
    },
    {
        "text": "Print a number, right?",
        "start": 5182.56,
        "duration": 0.93
    },
    {
        "text": "And so what should\nhappen is I should just--",
        "start": 5183.49,
        "duration": 3.122
    },
    {
        "text": "I should be able to march through this\narray, invoke each of those functions,",
        "start": 5186.612,
        "duration": 3.208
    },
    {
        "text": "and get back something\nthat counts, right?",
        "start": 5189.82,
        "duration": 2.86
    },
    {
        "text": "Basically?",
        "start": 5192.68,
        "duration": 1.547
    },
    {
        "text": "So let's see what happens.",
        "start": 5194.227,
        "duration": 1.083
    },
    {
        "text": "So I'm just going to access\nthat first one and invoke it,",
        "start": 5198.53,
        "duration": 2.9
    },
    {
        "text": "and we expect it to print out 0.",
        "start": 5201.43,
        "duration": 2.41
    },
    {
        "text": "So that there is one, a JavaScript\nprogrammer's worst enemy,",
        "start": 5207.57,
        "duration": 5.98
    },
    {
        "text": "because it's somewhat unexpected,\nand as we'll see in coming lectures,",
        "start": 5213.55,
        "duration": 3.59
    },
    {
        "text": "that is actually as expected.",
        "start": 5217.14,
        "duration": 2.75
    },
    {
        "text": "So I'll leave you guys on that\ncliffhanger for next time,",
        "start": 5219.89,
        "duration": 2.84
    },
    {
        "text": "and we'll go ahead and\nofficially end lecture.",
        "start": 5222.73,
        "duration": 2.6
    },
    {
        "text": "I'll stick around if you any questions.",
        "start": 5225.33,
        "duration": 3.27
    }
]